There was no mention made that unfreeze PINs were leaked. When you freeze your report with the three CRAs, you are given an unlock code or PIN needed to unfreeze it.
That's not clear from their help article about it [1], depending on what, in their definition, constitutes "proper identification forms":
"If you lose the PIN that was issued to you when you added the Security Freeze to your credit file, you may request a new one in writing. Please provide proof of identification, such as a copy of your driver's license, passport, birth certificate or other proper identification forms."
