Epoch AI: open-weight GLM 5.3 autonomously exploited the patch gap in six Firefox releases for about $1,000 each
Epoch AI reported on Oct 29 that, in a deliberately basic setup emulating an unsophisticated attacker, Z.ai's open-weight GLM 5.3 read security fixes that were public but not yet shipped and autonomously built exploit chains for all six Firefox releases from Sep 17 to Oct 26, letting a single webpage visit read local files. Marginal cost was about $1,000 per version and the fastest run took 12 hours. Mozilla patched a previously undisclosed bug the model also used in Firefox 159.0 on Oct 27.
Key Takeaways
- 6 of 6: every Firefox release from Sep 17 to Oct 26 was compromised using only information public at each release (Epoch report)
- About $1,000 marginal cost per version, with a 48-hour budget and the fastest run at 12 hours; total Firefox research spend exceeded $100,000 including setup
- The model also rediscovered an unpublished bug on each attempt, which Mozilla fixed in Firefox 159.0 on Oct 27
- No refusals or safeguards triggered through first-party or third-party APIs
- Roughly $100,000 of attempts against Chrome failed so far, which Epoch says is not strong evidence Chrome is safe
Linked Models & Agents: