If you add "firefox" into the "Dangerous keywords" section, it will delete pages that have the word "firefox" on the page itself, it won't check the URL.

Also, can you elaborate more on the search/form history? Do you mean preventing Firefox from autofilling on those pages? Or remove the search autocomplete history?

If you want it to delete pages that have "firefox" in the URL, then do the following steps:
1. Add the following into the "Dangerous domains" section (remove the quotes): ".*firefox.*"
2. Check off the "Regex dangerous domains" checkbox.

If you are still running into problems, please provide an example page if possible. It will help me find and fix the bug faster!

Also, can you elaborate more on the search/form history cleaning? Do you mean you want the extension to prevent Firefox from autofilling on those pages? Or do you mean that you want the search autocomplete to be deleted as well?