They are not blocked but are removed from the store, at least as far as I can read in my phone, without a login that the intercept forces on anyone who wants to read it.
The Intercept verified that all four add-ons are blocked in Russia. If the webpage for the add-on is accessed from a Russian IP address, the Mozilla add-on page displays a message: “The page you tried to access is not available in your region.” If the add-on is accessed with an IP address outside of Russia, the add-on page loads successfully.
It might be pedantic, but the difference I was trying to highlight was that it’s not blocked by the browser. It is (or was) blocked from being downloaded from the app marketplace.
The reason this is important is that the extension can still be installed, if you were to download it from elsewhere.
