Media reports claim Anthropic's Mythos model discovered 271 Firefox bugs. The reality is more nuanced. I dug into the actual article and bug reports to separate hype from substance.
Hi, my name is Tom Smykowski, I'm a staff full-stack engineer. I build and scale SaaS platforms to millions of users, working end-to-end from system architecture to frontend to mobile. On this blog I analyze tech news and separate AI hype from reality.
If you know me from my writing you know that I don't assume anything is true based on media reports. Usually what media report has little to do with reality. And especially now in the AI-bullshido era it's even more true, because most of the reports are fake, exaggerated or somewhere in between.
Now I think the most popular report is about Mythos, a model from Anthropic that supposedly found 271 bugs in Mozilla's browser. Is that true? Is Mythos so good it shouldn't be published?
Brian Grinstead, Christian Holler, and Frederik Braun wrote an article about it on May 7 claiming what I just wrote. The article is called "Behind The Scenes: Hardening Firefox with Claude Mythos Preview."
What The Bug Report Actually Shows
They mention for example such bug:
2027298 - Patches the color picker to simulate otherwise non-automatable user selection, then uses a synchronous input event to spin a nested event loop that re-enters actor teardown and frees the callback while it is still unwinding, triggering a content process UAF.
We also have a chart that says how many bugs Firefox team fixed each month, where in April 2026 it's 423 versus 25 in January 2026. I wonder what is the cause for that. Is that because people are fed up with Chrome downloading 4GB models without consent? Or maybe because Firefox team has some new funding so that they can work on bug fixes?
The full article includes my complete analysis of the actual vulnerability, the surprisingly simple bugfix, tests showing which AI models could detect this bug (spoiler: models from 2022 could find it), and practical guides for using AI in open source security work.