14 DAY TRIAL // Add-ons are a great way of expanding the functionality of a browser as well as adding features that would only interest a few people. Unfortunately, add-ons are also one of the easiest ways of slowing down your browser, adding instability, memory usage and so on.
Mozilla is in a delicate position when it comes to add-ons, on the one hand it welcomes all developers contributing to the ecosystem, on the other it has to ensure that users don't have problems because of add-ons.
Mozilla is now facing a somewhat common problem and decision, McAfee's SiteAdvisor 3.4.1, a security-focused add-on that has a history of causing problems in Firefox, is the cause of a rather huge memory usage issue in the browser.
Specifically, this version of the add-on doesn't free up memory when it should so the browser constantly needs more until, inevitably, it runs out.
The Mozilla contributor that discovered this suggests that the add-on should be blacklisted, which would disable it for all Firefox users. However, such drastic moves are not taken lightly.
McAfee is aware of the problem and is talking to Mozilla about it. In fact, it says that an update to the add-on is on its way.
In the meantime there are people at Mozilla as well as contributors that are asking that the current buggy version be blocked. The thing is, any issues with add-ons reflects poorly on Firefox.
If the browser crashes or is very slow, users will blame Firefox rather than the add-ons they've installed, or, in some cases, they didn't install but came with various other software, such as antivirus software, they did install.
Still, it seems that the issue doesn't affect enough people to have the add-on blocked. That said, McAfee SiteAdvisor has been blocked by Mozilla before.