We assumed this must be a nonsense rumor at first, but several reputable sites have now confirmed that CM Punk was indeed backstage tonight during the taping for Raw in his hometown of Chicago.
From what we can gather, Punk met with several talents (including The Miz, who he's had cross words with in the past) and Triple H. Nobody seems sure what was discussed, but it seems once Vince McMahon found out that Punk was on the premises, he had his head of security ask him to leave.
We have no idea why Punk showed up, but many believe it was simply an attempt to drum up some attention for his inevitable AEW return. Since he's still under contract with Tony Khan's company, the chances that he was there to discuss some kind of return are highly unlikely.
A fan filmed some video of Punk meeting with Tamina Snuka outside the venu.