: Because it is not available on the Official Firefox Add-on Store , it must be installed manually as an .xpi file. How to Install (Legacy Method)
In 2017, Mozilla released Firefox Quantum (version 57), which completely overhauled how extensions interact with the browser. Firefox dropped the legacy XUL/XPCOM extension framework—which Leethax relied on to deeply modify web pages—in favor of a more secure, sandboxed WebExtensions API. This change fundamentally broke the Leethax extension architecture. Security Risks and Malicious Imitations leethax net firefox extension
Installing the leethax extension on modern versions of Firefox is difficult because it relies on , which is no longer supported by modern browsers. : Because it is not available on the