Another possibility is that The Contessa is the one that leaked it to maintain some control over Blonsky, because of course he's on her recruiting wishlist. I mean he's not liable to be interested in coming to work for her if he's happy on his private groupie commune. (That's assuming of course that the "seven soulmates" isn't code for the Thunderbolts, and he's been clandestinely corresponding with The Contessa through the prison pen-pal system since he got transferred out of the SHIELD cryo-cell.)
That's my thought, too -- Val gets him into trouble so she can swoop in and "fix it for him" by offering to take him onto the Thunderbolts instead of back to a cryo cell. And as far as letter-writing, I doubt it would be the first time Val's catfished someone.