The vulnerability stems from the insecure use of os.path.join() in the job_browse route handler before passing the path to flask.send_file. The commit diff shows the fix replaced os.path.join() with werkzeug.utils.safe_join(), explicitly addressing path traversal. The 'path' parameter is user-controlled input that flows directly into this vulnerable path construction, making the job_browse function the entry point for the exploit. The combination of user-controlled input, unsafe path joining, and send_file usage creates the critical vulnerability.