Hi

This does not appear to be a question about Firefox, but possibly more of a question about the Symantec (the people that make Norton) product that you have installed.

You have not supplied a huge amount of information about the document, but I have done some research and I believe that this document relates to filtering controls in the Safari web browser. Depending on how you have set the parental controls, it may still be possible to download files that may come from a legitimate source and are not related to that content that parental filters may stop.

I hope this helps.

Triple posting. Continue here where you have two answers. https://support.mozilla.org/en-US/questions/1094630