The issue occured two days ago. After updating to Firefox 33.1, most of my extensions have dissappeared. List of extensions: NoScript, Adblock plus, Adblock plus pop-up a… (Lesen Sie mehr)
The issue occured two days ago. After updating to Firefox 33.1, most of my extensions have dissappeared. List of extensions: NoScript, Adblock plus, Adblock plus pop-up addon, Element hiding helper for Adblock plus, Multirow bookmarks toolbar, X-notifier, WOT, VKfox, вконтакте.ру downloader, Avast (switched off), Epubreader, Add to search bar.
My antivirus software: Avast 2015 free edition with all the updates.
Extensions which do not dissappear: Adblock plus, WOT, Epubreader, Avast online security (switched off).
What happens: yesterday I launched browser (Firefox 33.1) and found out that most of my extensions had dissappeared. I looked through Firefox system folders (Appdata/ and Program files/) - there were no signs of extensions, as if I had never installed them. I added them back. Surprisingly, all settings of extensions were okay. The next day this issue happened again. I thought it was some malware, so I ran antivirus checking. Avast found nothing. Next thing I thought of was: maybe Firefox does that itself? So, I installed all the extensions. Then I closed browser and immediately opened it again. Extensions were at their place. I thought that the issue was solved. Today, I switched my computer on, opened Firefox, guess what happened? Correct, no extensions (except for the four abovementioned ones). I re-installed Firefox, issue still exists. The only thing I found out - extensions dissappear with time. Today, my computer was switched on the whole day. I closed Firefox, left the computer for few hours. When I came back, there were no extensions, again.
What I am going to do now - check the system for malware again, with Dr.Web's CureIt utility. If it doesn't find anything, then, I will install the older version of Firefox and try it. Google Chrome works well, no problems with extensions (but I have only 2 installed for Chrome).
P.S. Almost forgot, bookmarks are okay, settings do not change, search engines are at their place too. But DuckDuckGo keeps appearing in list of search engines after uninstallation. So, I think that issue is in Firefox.