13 Jan 2022 - by 'Maurits van der Schee'
Firefox has a bug in its HTTP3 implementation causing the browser to hang or use a lot of CPU. You can temporarily disable HTTP3 as a workaround for the problem. You need to go to "about:config" and set "network.http.http3.enabled" to "false". In this post I'll show you how to do this using a script on Linux.
Disable HTTP3 (as a user preference):
echo 'user_pref("network.http.http3.enabled", false);' | tee -a \ $(find ~/.mozilla -name prefs.js | sed "s/prefs/user/g" | xargs)
Revert disabling HTTP3:
sed -i "/network.http.http3.enabled/d" \ $(find ~/.mozilla -name prefs.js | sed "s/prefs/user/g" | xargs)
You need to execute the script when Firefox is not running.
I hope this helps.
NB: I have heard people report that this bug is now resolved, so updating to the latest version might solve the problem as well.