Getting CORS error in hardened firefox( idk about others browsers) while installing plugins which cannot be resolved with addons too so need some practical suggestions :-)

[HakaishinShwet]

i am using hardened firefox and i have used every cors based addon and have tested some cors tested website with those addons enabled and cors test was passing but when i use same in my selfhosted setup with nginx proxy manager as reverse proxy manager and then with that if it try to login and install plugins then i am getting cors issue so if possible provide some alternate solutions if there are any instead of suggesting to use normal firefox or disabling particular flag of cors for browser