What is this circuit board mess?

[R3k1355]

Suspect this module is faulty, whipped it out and the circuitboard was kinda grubby.
Gave it a spray with some contact cleaner and have now got this odd white residue left.

Feels abit taky, is it some old glue or something?

Have a replacement part anyway so not worried if it's guffed, but would be good to know for the future if I shouldn't have tried what I did.

 

[Mole]

Looks like conformal coating, basically like a varnish that protects the board and components from the environment and prevents corrosion due to chemicals, moisture etc.
It's possible that the coating has reacted with the contact cleaner you sprayed on the board to clean it up