The Foundation discovers the second dimension. They've all read their Lovecraft, and they know that creatures from higher dimensions tend to enslave their inferiors. They take great pains NOT to do that, communicating in a kind and friendly way and showing them the wonders of three dimensions.
Little do they know, they have NO idea how 2-dimensional space works. By simply moving in three dimensions they wreak havoc on the fabric of 2D space, and the mere sight of their incomprehensible depths (literally) drives those of a weak constitution mad.
Eventually, they have enough, and using their equivalent of Scranton Anchors they fold the entire Site into two dimensions, killing everyone inside and almost causing an XK, were it not for the fact that the Minerva Inversion Machines (their Anchors) were primed to one specific place.
The only message they left was "YOU PLAYED WITH OUR WORLD, HOW DO YOU LIKE IT NOW?"
The Foundation is currently nervously poking the Keter classification at it with a stick.
The vague idea is that a scientist built a computer. He rigged it so that it could source and identify anything on the internet instantly. Then, he hooked the whole thing up to a reality nullifier. This is what happened:
Dr. [REDACTED]: Okay, B-203, delete the mug in my hand. (It is worth noting that Dr. [REDACTED] had posted images of the mug in question, along with many other subjects of the test, on his blog.)
SCP-XXXX-1: DELETING.
Dr. [REDACTED]: Holy shit, my mug! Ah, jeez, my best coat- but never mind that! My god, this is a miracle- Heavy breathing Okay. B-203, delete… delete the flowerpot on my desk.
SCP-XXXX-1: DELETING.
Dr. [REDACTED]: Giggling Woooah… What should I delete next? Disease? Death? Gasp I know. B-203… delete hatred.
SCP-XXXX-1: …ERROR, DOES NOT COMPUTE.
Dr. [REDACTED]: Yeah! Wait, what?
Dr. [REDACTED]: Uh… okay. B-203, delete war.
SCP-XXXX-1: …ERROR, DOES NOT COMPUTE.
Dr. [REDACTED]: Grr! B-203, delete racism!
SCP-XXXX-1: …ERROR, DOES NOT COMPUTE.
Dr. [REDACTED]: Why?!
SCP-XXXX-1: HATRED. WAR. RACISM. THESE ARE NOT OBJECTS. THESE ARE ABSTRACT CONCEPTS. MY DATABANKS CANNOT COMPUTE ABSTRACT CONCEPTS.
Dr. [REDACTED]: Just do it!
SCP-XXXX-1: NEGATIVE.
Dr. [REDACTED]: Do it!
SCP-XXXX-1: YOUR REQUESTS ARE CLOGGING MY DATABANKS. I AM PROGRAMMED TO DELETE THREATS TO MY DATABANKS.
Dr. [REDACTED]: Do it do it do it delete delete delete!
SCP-XXXX-1: THREAT TO DATABANKS DETECTED. DELETING THREAT.
So, we have an Anti-Antimeme: an idea that starts in millions of people and starts shrinking, eight people forgetting the info at a time.
No idea what the info is. May even blackbox it. Something to do with eight.
But I do know that as the information shrinks, the people who know start getting more and more aware that they are the only ones. They start becoming confused and paranoid, eventually forming a sort of cult. As the members of the cult forget, the members who forgot (known by the Eight Disciples (the name of the cult woah metaparentheses) as the Forgotten) are brutally murdered and their blood used to write the info (which suddenly becomes the "Eight Sacred Scriptures") down on scrolls and tapestries. It eventually comes down to one man, Guru Vito, who cannibalizes the eight remaining Forgotten, stabs himself eight times, and lives eight hours before instantly expiring, painting upon the walls with his own blood the same info eight hundred times. Later tests revealed that the info had minor cognitohazardous effects: people who knew it were just slightly more drawn to others who knew it, and slightly more adverse to people who didn't. At the start, which using Foundation computers they guess happened in August 8th, 1888, exactly 16,777,216 people knew of the anti-antimeme, AKA 8^8. The less people who knew, the more potent the effects were, especially if the number was a multiple of eight or contained the number eight. Writing it down also made it more potent, especially if the number of iterations was a multiple of eight, contained the number eight,or was written on things with dimensions that were multiples of eight or contained the number eight. Gatherings of people who knew also amplified the effects, espec-you get the idea?
The building was designated a quarantine shortly after, but it's implied that some crazy stoned people from one of the minor GOIs (maybe Fifthists) snuck in mere days before the quarantine and are currently in hiding, trying to spread the anti-antimeme.