ID: I202601241014
Status: idea
Tags: stayfree, browser extensions, CSS, firefox
stayfree firefox extension breaks css
StayFree Firefox Extension Update Breaking Site CSS (January 23, 2026)
ISSUE STATUS
As for right now, the issue is still present. (January 24)
If your websites suddenly started looking broken or strangely recolored in Firefox around January 23, 2026, you’re not alone. Many users have reported that the StayFree extension — specifically version 2.5.4 — introduced a major CSS issue that affects a wide range of websites.
The problem seems to come from a newly added file inside the extension, called ad-finder.css, which gets injected into every webpage. This file is unusually large and overwrites many site styles globally, causing colors, layouts, and entire design systems to break. The Chrome version of StayFree did not update alongside this Firefox release and is unaffected, suggesting the issue is confined to Firefox for now.
Users quickly began investigating the cause by extracting and reading the extension’s source code. Early checks suggest that the extension hasn’t been compromised, but several people have still chosen to uninstall it and reset their passwords as a precaution. Others noted that the added CSS file appears connected to some kind of ad-tracking feature or element detection system — possibly an overzealous content script gone wrong.
If your Firefox browsing experience looks off, you can confirm the issue by opening the browser’s developer tools and checking if the stylesheet moz-extension://…/content-scripts/ad-finder.css is loaded. Disabling this extension, or the stylesheet specifically, should immediately fix your site appearance.
At this stage, there’s no official patch or rollback from the developer. The current workaround is to disable or remove the StayFree extension until a fixed version becomes available. If you rely on StayFree, keep an eye on the extension’s update log — any new release should ideally remove or properly scope the problematic CSS.
Reports show that both large and small websites are impacted, including t3.chat, dbdiagram.io, stats.fm, Portainer and various smaller projects or company dashboards. For web designers and developers, this issue is particularly disruptive since it interferes with layout accuracy and site testing.
In short, if your Firefox suddenly makes websites “ugly” or unusable as of late January 2026 and you have StayFree installed, the update to version 2.5.4 is almost certainly the reason. Disable it for now, and wait for a developer fix.