Content blocking extensions need this permission to be able to inspect what content is requested and possibly block content if items are on a block list. Such extensions usually only inspect the request URL, but in theory extension can go deeper. It is up to you to decide whether to install the extension. *https://support.mozilla.org/en-US/kb/permission-request-messages-firefox-extensions *https://support.mozilla.org/en-US/kb/tips-assessing-safety-extension *https://blog.mozilla.org/addons/2018/02/01/understanding-extension-permission-requests/ Some extensions have a recommended label and such extensions have been more thoroughly inspected by the AMO team. You can consider uBlock Origin as a replacement for other ad-blockers to see if that works better (lower memory footprint). *https://addons.mozilla.org/firefox/addon/ublock-origin/