Not sure about how many to-date but it does occur every so often. This happens on countless sites so it's more so "who's doing it" versus any particular software being susceptible.
Make sure your password for ANY site is very long 18+ characters (or the max allowed) and very strong.
Example of strong password:
Example of weak password:
It's a simple phrase in a sense but is also 18 characters using both upper and lower case, numbers, and special characters such as ! and % which is much more secure than the one shown bottom which is simply all lower case and a plain word with a few numbers. The top password shown very strong and more secure than the one shown bottom.