Previous owner had the brakes done about two years ago. Fluid exchanged during frame swap a few months ago. No symptoms, no leaks, brakes feel great.
Today I noticed this corrosion on the vacuum brake booster near the master cylinder. Nothing is wet. It looks old. I just never noticed it before for some reason.
Thoughts? Maybe from a previous leak that has been repaired?
EDIT: clarified the location of the corrosion