Migration from outdated framework versions to current, actively maintained versions: Rails 4 to Rails 7 (intermediate upgrade path through 5 and 6, with dual-boot configuration using bootsnap to validate the upgrade before cutover), Node.js LTS upgrades (running ncu and depcheck to identify deprecated dependencies, Node 14 to 20 with CommonJS to ESM migration where applicable), Angular 8 to 17 (Nx migration executor with per-module upgrade validation), React class components to hooks (automated codemods via react-codemod for straightforward cases, manual migration for complex lifecycle patterns), PHP 7 to PHP 8 (Rector automated refactoring for deprecated constructs, strict type analysis with PHPStan), and Python 2 to Python 3 (2to3 automated conversion with manual review of encoding, integer division, and print function changes).
Security vulnerability remediation: OWASP Dependency-Check and Snyk run on the existing codebase to catalogue all dependencies with known CVEs before migration starts. The upgrade roadmap is prioritised by security severity, dependencies with critical CVEs are upgraded first, regardless of refactoring complexity. After migration, Dependabot or Renovate Bot is configured to propose automated dependency updates for future security patches so the codebase doesn't re-accumulate unsupported dependency debt.