As per the Forums Code of Conduct, under no circumstances should a hack or exploit be reported on the public forums. Because of the sensitive nature of hacks/exploits, posting on forums only ensures that other people are going to attempt to use them. Any poster who breaks this rule will have their thread deleted immediately and may receive further action, such as a restriction in posting privileges.
If you find an exploit or think someone is hacking into the game, please send a detailed e-mail to hacks@blizzard.com.
We thank you in advance for your reports. Reporting these issues is incredibly important, but at the same time please remember to report them through the secure channels.