The file-reading attacks combined clues in published security fixes with an unpublished flaw; Mozilla patched that flaw in Firefox 159, though Epoch has not tested whether the update blocks the attack.
By [RuntimeWire Staff](https://runtimewire.com/author/runtimewire-staff)
· Published
Primary source: [Hacker News](https://epoch.ai/publications/open-weight-models-patch-gap)
Why it matters #
The Firefox tests show that public security fixes can give an open-weight model enough information to build a working file-reading exploit before users receive the patch. Epoch's $1,000 estimate applies only after its harness was built, and Firefox 159's effectiveness against the full attack path remains unconfirmed.
Epoch AI researchers used Z.ai's open-weight GLM 5.3 model to build file-reading exploits against six Firefox releases, turning public security fixes into clues about vulnerabilities before those fixes reached users. The experiments show how quickly the "patch gap" can become a practical target: after building its test setup, Epoch estimated each successful attack cost about $1,000 in model API fees.…
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