Please explain the problem in detail. What happens? What are the exact error message(s) ?

Firefox will make changes to its own files. It can also save downloaded data and files. It should not do more than that.

Are you losing specific data ?

If that is the case, then in what location ?

Note that file saved to the OS temp folder aren't guaranteed to be kept when Firefox is closed.

Unfortunately, this is not an answer to my question. I want to know if Firefox could delete data on my hard drive if they wanted to.

heinzloehr said

Unfortunately, this is not an answer to my question. I want to know if Firefox could delete data on my hard drive if they wanted to.

Hello heinzloehr,

You, the user, can remove all browsing data from your hard drive, but your browser can't remove any data from your hard drive.