I have a Mastercard attached to the Paypal account, and so far 4 authorized transactions (I have paid to others) have been advised as charge backs from my bank. I called the Bank today to ask about it and advised they did not yet have any info but there were others calling about it.
Paypal has not replied to any contact, though I really should have called them.
I can't find anything online about it and it infuriates me that if its a known issue Paypal (or Mastercard) has not advised anything…except limited my account (though I do realise its to protect my account).
I'd just phone Paypal. Any time I've had to do so, there wasn't much of a wait.