That's just part of a webpage that you downloaded with Zotero that has some javascript that BitDefender doesn't like. Depending on the page, there's a good chance it's a false positive, but that's for you to evaluate.
To fix the issue, note the alphanumeric string of the folder it is in (like AY234SDG), paste that into Zotero's search in "All Fields and Tags" mode, then delete the corresponding attachment in Zotero and empty the Zotero trash.