Brian Grinstead

speaker

356 appearances 1 recordings 1 series first heard Jun 2026 last heard 22 Jun

Brian Grinstead’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 1 in all, peaking in Jun 2026 with 1.

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How I AI · How Claude Mythos found a 15-year-old bug in Mozilla Firefox | Brian Grinstead · 22 Jun 2026 podcast

So just another way to do it.

And so that's a very simple kind of, how do you just run this thing and find a problem in a source code file?

I think as we are running this on less trivial security issues, we found that we needed the actual harness that I was describing earlier.

And so we'll have an example of running that here, where it will basically do the same loop.

It's using an agent SDK, but it's gonna do, it has access to all of these tools.

And so it's gonna go through and read.

This'll take a while, so I'll switch over to a completed job here.

But it'll basically read, it'll do some tests, it'll run this HTML page as a, as a tester.

And then it'll say, yep, looks good.

Um, this is actually the verifier sub-agent has now returned some structured JSON saying, yep, I approved it.

Here's why this is a problem.

Here's sort of exactly how you would, uh, exploit it.

Here's the steps to reproduce and here's the security impact.

So at that point, you have the results, you have the bug that we could go and put this in our bug tracker system and give it to an engineer.

It does spin off a separate agent now to actually go and fix the bug.

And so it will go on and create it.

They'll Firefox and verify that the crash went away.

Yeah, and that's one of the things we've run into with scale.

Some of the sort of pre-packaged skills and workflows sort of assume that you can canvas the entire repository at once and find all the issues, and you just can't.

And so with Firefox, I would say.

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