Firefox 清除 HSTS 信息 [引自：https://security.stackexchange.com/questions/102279/can-hsts-be-disabled-in-firefox]：
- Click Profile Folder | Open Folder which should open your profile folder.
- Find file called
SiteSecurityServiceState.txtand open it
- Find the entry for your site url and remove it. Entry would looks something like –
github.com:HSTS 120 17242 1521194647604,1,1
- Make sure for above firefox is closed so that it does not overwrite it.
openssl s_client -connect host:443 -showcerts