What the hell is this, "Error Platform version...not compatible. Reinstall Firefox"???

[Raz]

Today on 28/5/26 while opening my PC I updated Firefox and after a few second saw this message:

After reinstalling Firefox now it is running ok with all my open Tabs intact!

But can someone please tell me WHY that message, in the first place?Never seen that before! Never!

[siffemcon]

See https://support.mozilla.org/en-US/questions/1468760#answer-1681010./

[Raz]

Thanks Siffemcon for that link! 

>> "This can happen in case security software was keeping a handle of some of the files in the Firefox program folder preventing Firefox from replacing all the files."

Yes I've a security software; but how can it keep a folder of those files in Firefox folder itself, instead of it's own folder?

[siffemcon]

"keeping a handle of some of the files in the Firefox program folder" simply means the security software had some of the FF files locked, so they couldn't be updated. What security software are you using?