they won’t be sent by infosec.pub directly, but other instances may send activities referencing content from infosec.pub, which will lead lemmy.ml to pull it from the source as well.
this includes for example posts and comments in lemmy.world communities, because lemmy.world will announce those to lemmy.ml.
to add to that, Lemmy currently does not handle site bans well if it’s not a home instance ban, as instances don’t keep track of which other instances have banned which users. this should get better with 1.0 though, as a PR to improve that was recently merged.
for now, there is a band-aid solution that federates community bans for all communities local to the instance the user got banned from, but that only includes communities that the user previously participated in, so they’ll still be able to participate in the local copies of other communities from the instance they’re banned from, it just won’t fully federate out.
there seems to be a codeberg mirror but it’s not updated continously: https://codeberg.org/LemmyNet
it’s literally explained in the post that it uses admin credentials