In a recent blog post, Mozilla has said that it’s identified the issue, and it’s begun rolling out a fix for users. “The fix will be automatically applied in the background within the next few hours. No active steps need to be taken to make add-ons work again.”
The company says that users shouldn’t try deleting and re-installing extensions, because it’ll remove any accumulated data. The fix that’s being rolled out won’t apply to Firefox ESR or Firefox for Android, and Mozilla says that it’s working to release a patch there as well.
Mozilla says that it’s using the Studies system to fix the error quickly, and if you’ve disabled that, you’ll need to re-enable it. The post runs users through the steps that they need to take to make sure it’s on, to check and make sure that it’s been applied. The company also says that it’s working on a fix that won’t involve that system.