I definitely expect a drawn out game of whack a mole as lemmy devs, instance admins and key contributors start seeing stuff like this pop up, and they develop tools or tech to mitigate abuse, until another exploit is found by bad actors, rinse and repeat.
Some say it’s an inherent flaw with federation/activitypub but I expect/hope it progresses the way other vulnerable tech has.
For example, in the early days of wifi it was pretty trivial to packet sniff (a practice that lets you peer into other folks network activity). Now most sites encrypt their transmitted data and while the packets could be sniffed over an unsecured network, the data within stays safe because it’s encrypted (assuming most sites that deal with sensitive data now encrypt, which in my experience, they do)
Furthermore WIFI as a technology has gone through many iterations, each one bringing with it better and stronger security, to the point where average Joe can setup a secure home network by following the quick start guide included with their router, which these days is essentially plug in, power on, choose a password, and authenticate with your devices.
I expect activitypub and fedi tech to develop in the same way: releasing patches and updates and ammending the standard to combat/mitigate abuse of an open federated platform., it’s gonna take time though.