GLM 5.3 turned published but unshipped Firefox security fixes into working one-click exploits. It compromised six Firefox releases between September 17 and October 26. Each exploit cost about $1,000 to develop. The model also found and used an unpublished vulnerability in each case. Mozilla patched the undisclosed flaw in Firefox 159.0 on October 27. The exploit could read local files from a user’s computer without interaction. Firefox has over 200 million active users. Similar attacks on Chrome have not yet succeeded. The model worked autonomously with no user input after initial instructions. No safeguards or refusals were triggered during the process. Open-source projects are particularly vulnerable to this attack vector.
What changed
Exploiting the patch gap required significant time, expertise, or access to frontier models.
What it unlocks
Building one-click exploits from published but unshipped security fixes using open-weight models.
- 6 Firefox releases exploited
- $1,000 cost per exploit
- 200M Firefox active users
- 12 to 48 hours per exploit
What you need to act on it
- GLM 5.3 access
- published but unshipped Firefox security fixes
Sources