I'm also experiencing the same problem as reported in https://addons.mozilla.org/en-US/firefox/addon/utm-remover/reviews/907936/ - if you have a link like https://out.reddit.com?url=https%3A%2F%2Fexample.com%3Futm_term=blah, the code in callback picks up the URL as one containing a UTM parameter, but removeUtmParams ends up removing nothing, since it's a parameter on the URL inside of the "url" query parameter, and the browser ends up in an infinite redirect loop.