Open-weight GLM 5.3 model built working Firefox exploits from unshipped patches

Epoch AI researchers showed that the open-weight GLM 5.3 model could turn Firefox security patches, visible in public code before reaching users, into working attacks. The resulting chains escaped the browser sandbox and read local files across six recent Firefox releases. Mozilla fixed the flaw in Firefox 159.0 on October 27. The same attack could not be reproduced in Chrome.