Again, and this is important: A bug is a bug. A “potential vulnerability” is a bug. A vulnerability is verifiable as having security implications with a proof of concept or other substantial evidence. Words matter. Bugs matter. It’s important to fix large amounts of bugs, just as it always has been, and has been done. Let that be impressive on its own, because it IS impressive. Mythos didn’t write 271 PoC for vulnera…
I was a bit confused by your definitions, but here's how Mozilla broke out [1] the 271, um, things: > As additional context, we apply security severity ratings from critical to low to indicate the urgency of a bug: > * sec-critical and sec-high are assigned to vulnerabilities that can be triggered with normal user behavior, like browsing to a web page. We make no technical difference between these, but sec-critical b…
In general, I would say that our use of "vulnerability" lines up with what jerrythegerbil calls "potential vulnerability". (In cases with a POC, we would likely use the word "exploit".) Our goal is to keep Firefox secure. Once it's clear that a particular bug might be exploitable, it's usually not worth a lot of engineering effort to investigate further; we just fix it. We spend a little while eyeballing things for the purpose of sorting into sec-high, sec-moderate, etc, and to help triage incoming bugs, but if there's any real question, we assume the worst and move on.
So were all 271 bugs exploitable? Absolutely not. But they were all security bugs according to the normal standards that we've been applying for years.
(Partial exception: there were some bugs that might normally have been opened up, but were kept hidden because Mythos wasn't public information yet. But those bugs would have been marked sec-other, and not included in the count.)
So if you think we're guilty of inflating the number of "real" vulnerabilities found by Mythos, bear in mind that we've also been consistently inflating the baseline. The spike in the Firefox Security Fixes by Month graph is very, very real: https://hacks.mozilla.org/2026/05/behind-the-scenes-hardenin...