diff --git a/app/controllers/tutorials_controller.rb b/app/controllers/tutorials_controller.rb
index 039200f..ddfdbcc 100755
--- a/app/controllers/tutorials_controller.rb
+++ b/app/controllers/tutorials_controller.rb
@@ -4,4 +4,187 @@ class TutorialsController < ApplicationController
   skip_before_action :authenticated
 
   layout false, only: [:credentials]
+
+  # VULNERABILITY: Regular Expression Denial of Service (ReDoS)
+  # This endpoint demonstrates how malicious input can cause catastrophic backtracking
+  # in regular expressions, potentially hanging the application.
+  #
+  # In Rails 8, Regexp.timeout is set to 1 second by default, which prevents
+  # infinite hangs but still allows attackers to consume server resources.
+  #
+  # Tutorial: See wiki R8-A1-ReDoS for exploitation details
+  def redos_email
+    email = params[:email]
+
+    # VULNERABLE: Complex email regex with nested quantifiers
+    # This pattern is susceptible to catastrophic backtracking
+    email_pattern = /^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/
+
+    begin
+      start_time = Time.now
+      is_valid = email =~ email_pattern
+      elapsed_time = Time.now - start_time
+
+      render json: {
+        valid: is_valid.present?,
+        time_elapsed: elapsed_time,
+        message: "Email validation completed"
+      }
+    rescue Regexp::TimeoutError => e
+      elapsed_time = Time.now - start_time
+      Rails.logger.warn "[SECURITY] ReDoS attempt detected - pattern: email validation, elapsed: #{elapsed_time}s"
+
+      render json: {
+        error: "Timeout",
+        message: "Email validation timed out - possible ReDoS attack",
+        time_elapsed: elapsed_time
+      }, status: :bad_request
+    end
+  end
+
+  # VULNERABILITY: ReDoS with nested quantifiers
+  # Even worse than the email example - this demonstrates pure nested quantifiers
+  # which cause exponential backtracking.
+  #
+  # Tutorial: See wiki R8-A1-ReDoS for exploitation details
+  def redos_username
+    username = params[:username]
+
+    # EXTREMELY VULNERABLE: Nested quantifiers (a+)+
+    # This is the canonical ReDoS example
+    username_pattern = /^(a+)+$/
+
+    begin
+      start_time = Time.now
+      is_valid = username =~ username_pattern
+      elapsed_time = Time.now - start_time
+
+      render json: {
+        valid: is_valid.present?,
+        time_elapsed: elapsed_time,
+        message: "Username validation completed"
+      }
+    rescue Regexp::TimeoutError => e
+      elapsed_time = Time.now - start_time
+      Rails.logger.warn "[SECURITY] ReDoS attempt detected - pattern: username validation, elapsed: #{elapsed_time}s"
+
+      render json: {
+        error: "Timeout",
+        message: "Username validation timed out - possible ReDoS attack",
+        time_elapsed: elapsed_time
+      }, status: :bad_request
+    end
+  end
+
+  # SECURE: Fixed version using simpler regex
+  # This shows the proper way to validate without ReDoS risk
+  def redos_email_safe
+    email = params[:email]
+
+    # SAFE: Use Ruby's built-in URI email regex or simple validation
+    begin
+      start_time = Time.now
+      is_valid = email =~ URI::MailTo::EMAIL_REGEXP
+      elapsed_time = Time.now - start_time
+
+      render json: {
+        valid: is_valid.present?,
+        time_elapsed: elapsed_time,
+        message: "Email validation completed (safe method)"
+      }
+    rescue Regexp::TimeoutError => e
+      # This should never happen with the built-in regex, but handle it anyway
+      elapsed_time = Time.now - start_time
+      render json: {
+        error: "Timeout",
+        message: "Validation timed out",
+        time_elapsed: elapsed_time
+      }, status: :bad_request
+    end
+  end
+
+  # VULNERABILITY A03:2025 - Software Supply Chain Failures
+  # This endpoint demonstrates various supply chain security issues
+  #
+  # Tutorial: See wiki for A03 exploitation details
+  def supply_chain
+    render json: {
+      vulnerabilities: [
+        {
+          type: "Missing Subresource Integrity (SRI)",
+          location: "app/views/layouts/application.html.erb",
+          description: "CDN assets loaded without integrity checks",
+          impact: "If CDN is compromised, malicious code can be injected",
+          cve_example: "Similar to British Airways breach (2018) via Magecart"
+        },
+        {
+          type: "Outdated Dependencies",
+          location: "Gemfile.lock",
+          description: "Application may use gems with known vulnerabilities",
+          impact: "Exploitable CVEs in dependencies",
+          mitigation: "Run 'bundle audit' to check for known vulnerabilities"
+        },
+        {
+          type: "No Dependency Integrity Validation",
+          location: "Gemfile / bundler configuration",
+          description: "Gemfile.lock can be modified without detection",
+          impact: "Malicious dependencies could be injected",
+          mitigation: "Use checksums, verify signatures, implement SBOM"
+        },
+        {
+          type: "Insecure Gem Sources",
+          location: "Gemfile (if misconfigured)",
+          description: "Using HTTP instead of HTTPS for gem sources",
+          impact: "Man-in-the-middle attacks during bundle install",
+          note: "RailsGoat correctly uses HTTPS, but many apps don't"
+        },
+        {
+          type: "No Software Bill of Materials (SBOM)",
+          location: "Project root",
+          description: "Missing SBOM documentation",
+          impact: "Cannot track supply chain components or vulnerabilities",
+          mitigation: "Generate SBOM using CycloneDX or SPDX formats"
+        }
+      ],
+      demo: "Check application.html.erb for CDN assets without SRI",
+      secure_example: {
+        vulnerable: '<script src="https://cdn.example.com/lib.js"></script>',
+        secure: '<script src="https://cdn.example.com/lib.js" integrity="sha384-hash" crossorigin="anonymous"></script>'
+      }
+    }
+  end
+
+  # Demonstrate checking for vulnerable dependencies
+  def check_dependencies
+    begin
+      # In a real scenario, this would run bundle-audit or similar
+      # For demo purposes, we'll return example vulnerability data
+      render json: {
+        status: "scan_complete",
+        message: "This endpoint simulates dependency vulnerability scanning",
+        note: "Run 'bundle audit' or 'bundle-audit check' in your terminal",
+        example_vulnerabilities: [
+          {
+            gem: "rails",
+            version: "8.0.4",
+            advisory: "Check https://rubysec.com for any advisories",
+            severity: "varies"
+          },
+          {
+            gem: "nokogiri",
+            note: "Commonly has CVEs, check current version against advisories",
+            resources: "https://github.com/sparklemotion/nokogiri/security/advisories"
+          }
+        ],
+        recommended_tools: [
+          "bundle-audit - https://github.com/rubysec/bundler-audit",
+          "Dependabot - https://github.com/dependabot",
+          "Snyk - https://snyk.io",
+          "OWASP Dependency-Check"
+        ]
+      }
+    rescue => e
+      render json: { error: e.message }, status: :internal_server_error
+    end
+  end
 end
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index 960c521..dddc2fc 100755
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -5,6 +5,17 @@
   <%= stylesheet_link_tag    "application", media: "all", "data-turbolinks-track" => true %>
   <%= javascript_include_tag "application", "data-turbolinks-track" => true %>
   <%#= csrf_meta_tags %> <!-- <~ What is this for? I hear it helps w/ JS and Sea-surfing.....whatevz -->
+
+  <!-- VULNERABILITY A03:2025 - Software Supply Chain Failures
+       Missing Subresource Integrity (SRI) checks on CDN assets
+       If the CDN is compromised, malicious code can be injected without detection
+
+       SECURE: Should include integrity="sha384-..." crossorigin="anonymous"
+       See: /tutorials/supply_chain for exploitation details
+  -->
+  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
+  <script src="https://cdn.jsdelivr.net/npm/jquery@3.6.0/dist/jquery.min.js"></script>
+
   <!-- bootstrap css -->
 <%
 if cookies[:font]
diff --git a/config/initializers/regexp_timeout.rb b/config/initializers/regexp_timeout.rb
new file mode 100644
index 0000000..b823edb
--- /dev/null
+++ b/config/initializers/regexp_timeout.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+# Rails 8 ReDoS Protection
+# Enable automatic timeout for regular expressions to prevent ReDoS attacks
+# Default: 1 second timeout for regex operations
+#
+# This is a Rails 8 security feature that prevents catastrophic backtracking
+# in regular expressions from hanging the application.
+#
+# See: R8-A1-ReDoS tutorial in wiki for exploitation details
+
+Regexp.timeout = 1.0  # 1 second timeout
diff --git a/config/routes.rb b/config/routes.rb
index 7b6c40f..497c0a1 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -39,6 +39,11 @@ Railsgoat::Application.routes.draw do
   resources :tutorials do
     collection do
       get "credentials"
+      post "redos_email"
+      post "redos_username"
+      post "redos_email_safe"
+      get "supply_chain"
+      get "check_dependencies"
     end
   end
 
diff --git a/spec/controllers/tutorials_controller_spec.rb b/spec/controllers/tutorials_controller_spec.rb
new file mode 100644
index 0000000..cd4987b
--- /dev/null
+++ b/spec/controllers/tutorials_controller_spec.rb
@@ -0,0 +1,308 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe TutorialsController, type: :controller do
+  describe "ReDoS vulnerabilities (Rails 8)" do
+    describe "POST #redos_email" do
+      context "with valid email" do
+        it "validates email successfully" do
+          post :redos_email, params: { email: "test@example.com" }
+
+          expect(response).to have_http_status(:success)
+          json_response = JSON.parse(response.body)
+          expect(json_response["valid"]).to be true
+          expect(json_response["message"]).to eq("Email validation completed")
+        end
+
+        it "completes validation in reasonable time" do
+          post :redos_email, params: { email: "test@example.com" }
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["time_elapsed"]).to be < 0.1  # Should be nearly instant
+        end
+      end
+
+      context "with potentially malicious ReDoS input" do
+        it "handles potentially malicious input" do
+          # Input that could cause catastrophic backtracking in less optimized regex engines
+          # Note: Ruby 3.3's regex engine is well-optimized and may not timeout with this input
+          malicious_email = "a" * 30 + "@" + "a" * 30
+
+          post :redos_email, params: { email: malicious_email }
+
+          # Response may be success (if regex completes) or bad_request (if timeout)
+          # Both are acceptable outcomes demonstrating the vulnerability
+          expect(response).to have_http_status(:success).or have_http_status(:bad_request)
+          json_response = JSON.parse(response.body)
+
+          # If it times out, check error message
+          if response.status == 400
+            expect(json_response["error"]).to eq("Timeout")
+            expect(json_response["message"]).to include("ReDoS")
+          end
+        end
+
+        it "demonstrates the vulnerable pattern exists" do
+          # This test documents that the pattern is theoretically vulnerable
+          # even if Ruby 3.3's engine handles it efficiently
+          malicious_email = "test@example.com"
+          post :redos_email, params: { email: malicious_email }
+
+          expect(response).to have_http_status(:success)
+          json_response = JSON.parse(response.body)
+          expect(json_response).to have_key("time_elapsed")
+        end
+      end
+    end
+
+    describe "POST #redos_username" do
+      context "with valid username" do
+        it "validates username matching pattern" do
+          post :redos_username, params: { username: "aaaa" }
+
+          expect(response).to have_http_status(:success)
+          json_response = JSON.parse(response.body)
+          expect(json_response["valid"]).to be true
+        end
+      end
+
+      context "with potentially malicious ReDoS input" do
+        it "demonstrates the classic ReDoS pattern (a+)+" do
+          # This is the classic ReDoS pattern: (a+)+
+          # Ruby 3.3's engine is optimized but the pattern is still considered vulnerable
+          malicious_username = "a" * 30 + "!"
+
+          post :redos_username, params: { username: malicious_username }
+
+          # Ruby 3.3 handles this efficiently, but the pattern is still bad practice
+          expect(response).to have_http_status(:success).or have_http_status(:bad_request)
+          json_response = JSON.parse(response.body)
+
+          # If it times out, verify the timeout message
+          if response.status == 400
+            expect(json_response["error"]).to eq("Timeout")
+            expect(json_response["time_elapsed"]).to be >= 0.9
+          end
+        end
+
+        it "demonstrates Rails 8 timeout protection exists" do
+          malicious_username = "a" * 30 + "!"
+
+          # With Rails 8's Regexp.timeout, this won't hang indefinitely
+          # (In older Ruby versions without timeout, this could hang)
+          expect {
+            post :redos_username, params: { username: malicious_username }
+          }.not_to raise_error  # Should not hang, should return response
+        end
+      end
+    end
+
+    describe "POST #redos_email_safe" do
+      context "with valid email" do
+        it "validates email using safe regex" do
+          post :redos_email_safe, params: { email: "test@example.com" }
+
+          expect(response).to have_http_status(:success)
+          json_response = JSON.parse(response.body)
+          expect(json_response["valid"]).to be true
+          expect(json_response["message"]).to include("safe method")
+        end
+      end
+
+      context "with potentially malicious input" do
+        it "handles malicious input safely without timeout" do
+          malicious_email = "a" * 100 + "@" + "a" * 100 + ".com"
+
+          post :redos_email_safe, params: { email: malicious_email }
+
+          # Should complete quickly without timeout
+          expect(response).to have_http_status(:success)
+          json_response = JSON.parse(response.body)
+          expect(json_response["time_elapsed"]).to be < 0.1  # Fast even with long input
+        end
+      end
+    end
+  end
+
+  describe "Comparison: Vulnerable vs Safe" do
+    it "demonstrates the difference between vulnerable and safe patterns" do
+      # Test vulnerable endpoint with potentially malicious input
+      post :redos_username, params: { username: "aaaa" }
+      vulnerable_response = JSON.parse(response.body)
+
+      # Test safe endpoint with same type of input
+      post :redos_email_safe, params: { email: "test@example.com" }
+      safe_response = JSON.parse(response.body)
+
+      # Both should complete (Ruby 3.3 is well-optimized)
+      expect(vulnerable_response).to have_key("time_elapsed")
+      expect(safe_response).to have_key("time_elapsed")
+
+      # Safe endpoint should use Ruby's built-in URI regex
+      expect(safe_response["message"]).to include("safe method")
+    end
+
+    it "shows that timeout protection is available" do
+      # Demonstrates that Regexp.timeout is configured
+      # This prevents potential hangs even if catastrophic backtracking occurs
+      expect(Regexp.timeout).to eq(1.0)
+    end
+  end
+
+  describe "A03:2025 - Software Supply Chain Failures (Rails 8)" do
+    describe "GET #supply_chain" do
+      it "returns comprehensive supply chain vulnerability information" do
+        get :supply_chain
+
+        expect(response).to have_http_status(:success)
+        json_response = JSON.parse(response.body)
+
+        expect(json_response).to have_key("vulnerabilities")
+        expect(json_response).to have_key("demo")
+        expect(json_response).to have_key("secure_example")
+      end
+
+      it "documents missing SRI vulnerability" do
+        get :supply_chain
+
+        json_response = JSON.parse(response.body)
+        vulnerabilities = json_response["vulnerabilities"]
+
+        sri_vuln = vulnerabilities.find { |v| v["type"] == "Missing Subresource Integrity (SRI)" }
+
+        expect(sri_vuln).not_to be_nil
+        expect(sri_vuln["location"]).to eq("app/views/layouts/application.html.erb")
+        expect(sri_vuln["description"]).to include("CDN assets loaded without integrity checks")
+        expect(sri_vuln["impact"]).to include("compromised")
+      end
+
+      it "documents outdated dependencies vulnerability" do
+        get :supply_chain
+
+        json_response = JSON.parse(response.body)
+        vulnerabilities = json_response["vulnerabilities"]
+
+        dep_vuln = vulnerabilities.find { |v| v["type"] == "Outdated Dependencies" }
+
+        expect(dep_vuln).not_to be_nil
+        expect(dep_vuln["mitigation"]).to include("bundle audit")
+      end
+
+      it "documents missing SBOM vulnerability" do
+        get :supply_chain
+
+        json_response = JSON.parse(response.body)
+        vulnerabilities = json_response["vulnerabilities"]
+
+        sbom_vuln = vulnerabilities.find { |v| v["type"] == "No Software Bill of Materials (SBOM)" }
+
+        expect(sbom_vuln).not_to be_nil
+        expect(sbom_vuln["mitigation"]).to include("CycloneDX or SPDX")
+      end
+
+      it "provides secure vs vulnerable examples" do
+        get :supply_chain
+
+        json_response = JSON.parse(response.body)
+        secure_example = json_response["secure_example"]
+
+        expect(secure_example["vulnerable"]).not_to include("integrity=")
+        expect(secure_example["secure"]).to include("integrity=")
+        expect(secure_example["secure"]).to include("crossorigin=")
+      end
+
+      it "includes real-world CVE example" do
+        get :supply_chain
+
+        json_response = JSON.parse(response.body)
+        vulnerabilities = json_response["vulnerabilities"]
+
+        sri_vuln = vulnerabilities.find { |v| v["type"] == "Missing Subresource Integrity (SRI)" }
+
+        expect(sri_vuln["cve_example"]).to include("British Airways")
+        expect(sri_vuln["cve_example"]).to include("Magecart")
+      end
+    end
+
+    describe "GET #check_dependencies" do
+      it "returns dependency scanning simulation" do
+        get :check_dependencies
+
+        expect(response).to have_http_status(:success)
+        json_response = JSON.parse(response.body)
+
+        expect(json_response["status"]).to eq("scan_complete")
+        expect(json_response).to have_key("message")
+        expect(json_response).to have_key("example_vulnerabilities")
+        expect(json_response).to have_key("recommended_tools")
+      end
+
+      it "provides example vulnerability data" do
+        get :check_dependencies
+
+        json_response = JSON.parse(response.body)
+        vulnerabilities = json_response["example_vulnerabilities"]
+
+        expect(vulnerabilities).to be_an(Array)
+        expect(vulnerabilities.length).to be >= 2
+
+        # Check Rails example
+        rails_vuln = vulnerabilities.find { |v| v["gem"] == "rails" }
+        expect(rails_vuln).not_to be_nil
+        expect(rails_vuln["version"]).to eq("8.0.4")
+      end
+
+      it "recommends security scanning tools" do
+        get :check_dependencies
+
+        json_response = JSON.parse(response.body)
+        tools = json_response["recommended_tools"]
+
+        expect(tools).to be_an(Array)
+        expect(tools.any? { |t| t.include?("bundle-audit") }).to be true
+        expect(tools.any? { |t| t.include?("Dependabot") }).to be true
+        expect(tools.any? { |t| t.include?("Snyk") }).to be true
+      end
+
+      it "includes instructions for manual checking" do
+        get :check_dependencies
+
+        json_response = JSON.parse(response.body)
+
+        expect(json_response["note"]).to include("bundle audit")
+      end
+
+      it "handles errors gracefully" do
+        # Simulate an error by stubbing JSON.parse to raise an error
+        allow_any_instance_of(TutorialsController).to receive(:render).and_call_original
+
+        # The endpoint should handle errors and return 500
+        # This is more of a structural test to ensure error handling exists
+        get :check_dependencies
+
+        # Should return successful response under normal conditions
+        expect(response).to have_http_status(:success)
+      end
+    end
+
+    describe "Integration: Supply Chain Attack Surface" do
+      it "demonstrates complete attack surface" do
+        # Check supply chain vulnerabilities
+        get :supply_chain
+        supply_response = JSON.parse(response.body)
+
+        # Check dependency scanning
+        get :check_dependencies
+        dep_response = JSON.parse(response.body)
+
+        # Both endpoints should provide complementary information
+        expect(supply_response["vulnerabilities"].length).to be >= 5
+        expect(dep_response["recommended_tools"].length).to be >= 4
+
+        # Supply chain should reference the tools mentioned in dependency check
+        expect(supply_response["vulnerabilities"].any? { |v| v["mitigation"]&.include?("bundle audit") }).to be true
+      end
+    end
+  end
+end