It's the Stripe patch that it keeps telling me is available even though it is already installed.
Here's the screen with the message open, and the screen showing my list of messages.
I delete the message that tells me the Stripe update is available, and within an hour or two, the next time I log in, there is a brand new copy of that message in my messages folder and the little balloons icon for messages has a red numeral 1 to tell me that I have a new message.
I've deleted it at least five times so far, and it keep coming back!
The third screencap shows that I already have version 1.0.5 of the Stripe extension installed.