With the Firefox 135.0.1 update for Windows, macOS, and Linux, Mozilla has fixed several security vulnerabilities along with some non-security-related bugs, which include some browser crash issues and problems with browser history after an update.
Mozilla’s 2025-12 Security Advisory shows only one fixed security vulnerability, but it’s a summarized entry that describes an unspecified number of identical or similar flaws. Mozilla states a “high” risk rating because these vulnerabilities lead to a “potentially exploitable crash.” There are no known attacks on Firefox users that exploit these vulnerabilities.
As Mozilla doesn’t release security updates with the same regularity between major versions as Google does with Chrome, it’s possible there’s some other reason for pushing this update. Maybe they just wanted to fix the other bugs that were addressed.
Other bugs fixed in the update
Among the problems fixed in Firefox 135.0.1 is one with the browser history. After updating from an older version, closed windows and tabs can’t be restored and are therefore lost.
If you’ve installed an OpenSearch search engine with an oversized icon, the search in Firefox stops working in some cases. Context menus also sometimes stop working as intended. If a web page has internal links, Firefox may jump to the wrong place on the page when you click on such a link. Incorrect behavior can also occur with mousemove events for selection menus. German blogger Sören Hentzschel also found a fixed for Mozilla not receiving all the necessary information in crash reports sent by Firefox with the user’s permission.
If you don’t have this Firefox update yet, you can install it manually by navigating to Help > About Firefox. Mozilla plans to release the next version, Firefox 136, on March 4, 2025.
Further reading: Firefox adds AI to browser and surprises no one