fix(security): restrict external links to web URLs

[DysektAI]

What changed

• add one ExternalLinkLauncher entry point that accepts only absolute HTTP(S) URLs
• route surviving UI, logger, and WebView external-link launches through it
• add regression coverage for executable paths, UNC paths, local files, custom protocols, malformed URLs, and valid web URLs

Why

Several link targets originate in remote catalog data and were passed directly to Windows ShellExecute. That permits non-web targets such as local executables, UNC paths, and registered protocol handlers to reach the shell.

Impact

Normal HTTP(S) links continue opening in the default browser. Unsafe or malformed targets are logged and ignored without taking down the WebView render path.

Validation

• dotnet tool restore
• dotnet csharpier check .
• dotnet build RatScanner.sln --no-restore — 0 warnings, 0 errors
• dotnet test RatScanner.sln --no-build --no-restore — 246 passed

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Summary by cubic

Restricts external links to absolute HTTP(S) URLs and routes all opens through a safe ExternalLinkLauncher. Strengthens logging by redacting rejected targets and sanitizing accepted ones to prevent data leaks.

• Bug Fixes
  • Added ExternalLinkLauncher with strict URL validation and safe open.
  • Routed UI, logger, and WebView link opens through the launcher.
  • Logging: redacts rejected targets as "" or ""; for accepted links removes credentials, queries, fragments, and control chars; omits exception details.
  • Tests cover URL filtering and log redaction for both rejected and accepted targets.

^{Written for commit cf2dbb8. Summary will update on new commits.}

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

A shared ExternalLinkLauncher validates absolute HTTP(S) URLs, sanitizes warning targets, launches approved links through the shell, and suppresses failures. Logger, page, and hyperlink-navigation paths now delegate to it, with tests covering accepted, rejected, and failed launches.

External link safety

Layer / File(s)	Summary
Launcher validation and tests src/App/ExternalLinkLauncher.cs, tests/RatScanner.Tests/ExternalLinkLauncherTests.cs	Adds absolute HTTP(S) validation, sanitized warning handling, shell launching, and tests for safe, unsafe, malformed, missing, and failed launches.
Application link integration src/App/Logger.cs, src/App/Pages/App/Credits.razor, src/App/Pages/App/Index.razor, src/App/View/BlazorUI.xaml.cs	Replaces direct process launches with ExternalLinkLauncher.Open across logger, page helpers, and hyperlink navigation.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant UI
  participant ExternalLinkLauncher
  participant Shell
  UI->>ExternalLinkLauncher: Open(url)
  ExternalLinkLauncher->>ExternalLinkLauncher: Validate absolute HTTP(S) URL
  ExternalLinkLauncher->>Shell: Start validated URL

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 18.18% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly captures the main change: restricting external links to safe web URLs.
Description check	✅ Passed	The description matches the change set and accurately summarizes the safe-linking refactor and tests.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/external-link-safety

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