I am wondering why Avast didn't find it because that is my primary Antivirus Program? The program is automatically updated.
No security program have 100% detection or zero false positives
Did you consider that Windows Defender may be the one that is wrong?
anyway, you give no info
-what files was detected
-at what location ... full file path (from detection name it may be a mail attachment ?)
-have you tested detected file at
www.virustotal.com ... post link to scan result
I also ran Malwarebytes AdwCleaner and it did not find this either.
This is made to clear browser crap