Firefox 68.6 / 8 help + cookie editing addons

Hello every 1 . I really need to get version 68.6 or 68.8 of the firefox , but when im trying to install one from any mirrors or else its always says “broken file” where can i find 1 ?
Need it mostly for cookie editing addon


I don’t think this is the right forum for this question but have you tried

What add-on works in Firefox 68 but not in current versions of Firefox, can you give its fuller name or its ID?