Re:Firefox now blocks Ad-filtering add-ons (uBlock Origin, A...
by zinekeller on Sunday March 20, 2022 @04:27AM
(#30741075)
Also, I believe this is related to a legal precedent against ad-blocking in China (https://adguard.com/en/blog/china-blocks-ad-blocking.html), which AdGuard notes that is ironic given that UC Browser has adblockers.
1) Mozilla China is practically an independent organization and their Firefox builds have been quite different from "Normal" Firefox for a long time.
2) That error code is 451, "Unavailable For Legal Reasons", usually used to indicate government censorship.