Yes this morning 4 accounts decided to send spam PM's to many accounts. I have deleted all the private messages however if you had email alerts for private messages enabled you received an email unfortunately.
What I've do so far...
Banned the accounts & ip's sending the spam messages
Deleted the messages they sent
Increased rate limit (from 20 sec to 5 min) on new accounts on sending private messages
Stopped email alerts for private messages as default in account options