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Mastodon fixes critical “TootRoot” vulnerability allowing node hijacking
(arstechnica.com)
This is a most excellent place for technology news and articles.
Nope, other than the use of the ActivityPub standard to communicate information, Mastodon and Lemmy are entirely separate pieces of software. Whether Lemmy, Kbin and similar also have vulnerabilities that would allow for a similar exploit are dependent on how they've been designed.