As Buzzfeed reports, the first large blog to get hit was The Daily Dot, and this helped spread the malicious and offensive spam post to many other blogs. Just paying a visit to an infected page can see your account infected itself, it would seem.
Apparently this is the work of a hacking organisation which goes by the name of the GNAA.
This thing is still spreading, and as Buzzfeed notes, if you’re a Tumblr user, the best thing to do at the moment is just to avoid the site until the powers-that-be implement a fix and clear this mess up.
An hour ago, Tumblr acknowledged the issue on its Twitter account: “We are aware that there is a viral post circulating on Tumblr. We are working to resolve the issue as swiftly as possible. Thank you.”