Developers at Mozilla pushed out Firefox 41 this week and brought some much needed relief to AdBlockPlus users by finally fixing a 14-year old bug in the browser.

Developers at Mozilla pushed out Firefox 41 this week and brought some much needed relief to Adblock Plus users by finally fixing a 14-year old bug in the browser.

The update addresses a longstanding issue with how the browser handles memory usage by the add-on. Previously the browser created too many “style sheets” for Adblock Plus users, something that was causing small spikes in memory usage.

Adblock Plus is far and away Firefox’s most popular extension, boasting over 21,000,000 users, according to Firefox’s add-ons page. The second most popular extension only has 5,000,000 users.

While Mozilla doesn’t mention the fix in the release notes for Firefox 41, Ben Williams, Adblock Plus’ Operations and Communications Manager acknowledged the update with a post on the company’s blog Wednesday.

“[Users] can now rest easier and browse just that much quicker, because last week a Mozilla developer patched a 14-year-old bug,” Williams wrote, “Now Firefox uses about the same amount of memory whether you’re running ABP or not.”

As Williams points out, incredulously, a Bugzilla ticket related to the issue (bug 77999) was first filed more than 14 years ago, on April 27, 2001. According to Nicholas Nethercote, an Australian Mozilla programmer, Cameron McCormack, a Firefox developer patched the issue over the summer by adding data structures that share the results of cascading user agent style sheets. It wasn’t until Tuesday, when Mozilla released the stable version of Firefox 41, that the patch went live however.

The latest build of the browser also addresses a handful of bugs, including eight reported by security researcher Ronald Crane. The bugs, which were dug up during code inspection, included several potential memory safety issues according to a Mozilla Foundation Security Advisory.

“These do not all have clear mechanisms to be exploited through web content but are vulnerable is a mechanism can be found to trigger them,” the advisory, which is marked high impact, reads.

In addition to Crane’s bugs, Firefox 41 also fixes a smattering of other issues, including memory safety errors, use-after-free vulnerabilities, buffer overflows, and other bugs that could let attackers run arbitrary code, and gather sensitive data, among other consequences.

The latest iteration of the browser also incorporates Firefox Hello, the browser’s WebRTC-based communications system, enhanced IME support, user personalization, and enhanced box-shadow rendering performance.