Hello everyone, before do new post here, i has been tried feedback to Firefox China Forum, but the forum's staff always says "i'm tried and all works fine", so i have no way but ask here for some help. (original post: http://mozilla.com.cn/thread-421541-1-1.html) what is "qzone.qq.com"? almost biggly social website in China just like facebook, it made by China company who named Tencent. i cant remember from which version of firefox has this issue, maybe from firefox 62.0. "qzone.qq.com"'s css was broken (just as 1st pic) due to "iframe cross-origin issue", but in msedge or chrome has no this issue. in developer tools, it shows following errors: (just as 2nd pic) 1. SecurityError: Permission denied to access property "g_V" on cross-origin object 2. TypeError: G_Param is undefined 3. TypeError: QZONE.namecard is undefined but i found the iframe are the same domain as parent frame, both “user.qzone.qq.com” (just as 3rd pic), but when you open the iframe src in new tab, all works fine. (just as 4th pic). i dont know how to resolve that, i tried reinstall windows system, reinstall firefox with no plugin installed, change my isp. but all not working. thanks for eveyone's help Pekaikon Norckon