I asked a similar question recently, and was told to uncheck the site preferences box in Clear Recent History. I did that and it partly worked - but it doesn't explain why or how FF should be effecting security measures I'd put in place to protect my PC from spyware and malware.

My "site preference" has never been checked off and this only started happening in the past few weeks. I also have the "Everything" delete on at the top of that page.

I don't think that is the cause.