It's of course a bug of your antivirus, that has got a false positive and, it seems to be so bugged that doesn't even recognize the industry-standard "Taggant" digital signature we sign all our executables with, which is a way to help proper antivirus product to not mistakenly flag legit software as a threat.
We sign everything with two digital signatures: Authenticode from Microsoft the the software Taggant, which is specific to prevent false positive so, there's no excuse for antivirus vendors to keep making such mistakes.
Add the whole Addon Manager folder to the antivirus Exclusion and run the update again.
