Hi, yes if the person who makes it adds bad code between samples on the https://addons.mozilla.org/firefox/ If you run into any there is a Abuse link on every page of Extensions/add-ons and Themes. leethax is not a Authorized Extension that is supported by the above URL. Any extensions/addons that are not in the above URL when searched should be treated as suspect. If you have a issue with that or their claims you can report them from the 3 Bar Menu --> Help --> Report Deceptive Site. Report spam, paid links, or malware within Google's search results https://support.google.com/webmasters/answer/93713?hl=en https://safebrowsing.google.com/safebrowsing/report_phish/?hl=en