We’ve mentioned this before, but it’s worth repeating occasionally to ensure the message gets out.
Certain guitar and bass straps do not get along well with certain types of finishes, particularly nitrocellulose lacquer. To keep your instrument looking its best, remove the strap when you’re not playing, and if you do leave the strap on, make sure that it is not laying across a finished part of the instrument. You may come back to find the finish discolored or otherwise damaged.