The vulnerability exists in route handlers processing '/workspace' endpoints. Both locations shown in the diff (lines 157 and 185 in routes.ts) construct filePath using path.join(workspaceDir, file) without verifying the resulting path remains within workspaceDir. Attackers could supply 'file' parameters with directory traversal sequences (../../) to access arbitrary files. The patch added critical containment checks using filePath.includes(workspaceDir), confirming these were the vulnerable points. The functions handle user-supplied filenames directly and return file contents, making them the clear injection points for path traversal.