If you can tolerate 1) the low user count, 2) it not being a recommended extension (not "monitored" by Mozilla), 3) a pseudonymous author, and that 4) all checked URLs are submitted to the author's proxy server, this is one of the most comprehensive malware and phishing-page blockers. The most intrusive permission, "Access your data for all websites," is optional. Search the MalwareTips forum for more comments — the extension author also contributes there.

Amazing extension! The ability to choose security providers and such a rich selection of trusted vendors is an ultimatum defense against any browser threats!