I found this on StackOverflow and I found it interesting... If this is possible wouldn't this be so useful to the feds?
It asks can you get the server ip address from a mysql database for a login system, https://stackoverflow.com/q/19338858/2177766
I'm saying that if a hidden service is running say WordPress for an example would it be possible to SQL Inject the MySQL Server into giving you the public IP Address. How badly could this affect your anonymity of your hidden service?