Today I received an email from the department IT office, saying my backup drive has multiple suspected infected files. I found all of them were webpage snapshots taken by Zotero. I never used these snapshots so I disabled this option for the future. I also removed all the old snapshots using the method described here. Basic steps: Menu -> Edit -> advanced search -> Attachment File Type – is – Web Page -> Create saved search (this will create a folder with the search results) -> Go to the saved search and select all. Note now only snapshots are selected -> right click and move items to trash -> right click the trash icon -> empty.