Same happened to me, I was just casually surfing the web when I got a popup window informing me Opera has blocked malicious extension, or something like that. Happened maybe two hours ago.
Tampermonkey and it's scripts (that now I can't retrieve, I see no obvious way to get them back and install another script manager temporarily) are pretty much essential for me so I'd like to get it back if possible.
Opera version: 57.0.3098.110
Windows version: Windows 10 1809 x64
Tampermonkey version 4.7.54