Researchers Talal Haj Bakry and Tommy Mysk discovered a rare method to bypass macOS protections and replace the main executable of any web‑downloaded app with malicious code. The exploit requires a very specific sequence:ohen the务 app must be downloaded, launched at least once, archived with .tar, deleted, then extracted again. Because the app remains signed and notarized, macOS treats the re‑unarchived version as the same trusted application, allowing it to run unchecked.

The vulnerability affects only non‑App Store apps. It demands that the attacker already has code execution on the target machine, usually through a previous compromise. Apple views it mainly as a social‑engineering challenge rather than a direct bypass of security mechanisms, noting that the user would need to perform multiple deliberate steps.

Apple recommends avoiding the trick by installing only apps from the Mac App Store or, if a web‑downloaded app must be removed, by re‑downloading it instead of archiving. The researchers suggest macOS add a re‑verification step after an app is extracted from a tar archive to close the loophole.

Overall, the flaw is unlikely to be widely exploited without prior access but illustrates a subtle weakness in how signed apps are validated after file manipulation.