Nearly 9,000 Tumblr accounts have reportedly been infected by the virus. The virus is evidently spread when infected users see this message on their Tumblr page. When a user clicks on the message, the message is posted to his blog, and other users who visit an infected Tumblr site while logged in will have their blogs infected as well. An anti-blogging group calling itself the Gay Nigger Association of America (GNAA) has claimed responsibility.

Posting is currently disabled:

Tumblr users are warning each other to log out of their accounts and avoid clicking suspicious links:

Tumblr has released a brief official statement:

There is a viral post circulating on Tumblr which begins “Dearest ‘Tumblr’ users”. If you have viewed this post, please log out of all browsers that may be using Tumblr immediately. Our engineers are working to resolve the issue as swiftly as possible.  Thank you.

And sent this message via Twitter: