The security patches add symlink validation checks to the process middleware in lib/middleware.js. The first commit (51cfb247) directly modifies exports.process to add lstat/readlink checks, indicating this was the vulnerable entry point that previously served files without validation. Subsequent commits refactor the check into dedicated middleware, but the core vulnerability existed in the file processing flow handled by exports.process prior to these mitigations. This function would appear in runtime profiles when serving malicious symlinks as it's the main asset pipeline handler.