Just over a week ago, Mozilla’s memory team discovered major leaks caused by the McAfee SiteAdvisor 3.4.1 add-on. A bug was filed, and six days later the McAfee team released version 126.96.36.199, which fixed the major leaks.
The Add-ons Team generally will not block legitimate add-ons without consulting with their developers first and giving them a reasonable amount of time to analyze and fix whatever problem is discovered. We have found that developers of legitimate, widely-used add-ons are usually more than happy to work with us in finding resolutions to problems and ensuring a smooth experience for users. As expected in this case, the McAfee team kept close communications with us and provided a pre-release version for us to test in advance. The partially fixed version was released less than a week later.
Version 188.8.131.52 doesn’t fix all the memory leaks, but it does fix the most serious ones. The remaining leaks are being tracked on bug 729608. At this point it is unclear if the remaining memory leaks are caused by McAfee’s code or Firefox bugs. We will keep you up-to-date on any major developments.