Haven’t had a new insertion in the last week.
I did have weird users when I first noticed, but after deleting all of them and changing the password on the admin account, I’ve gotten at least one more.
The only active plugin I have is akismet
The theme I use is custom, and has been there for two years without problem (until recently).
Same code, injected into the middle of some, but not all, new posts, also on 2.7.1, although recently updated from 2.5 and I wouldn’t swear that it didn’t start in 2.5
