Paint
Bubbling paint is the finish letting go of wet material.
Owners often scrape and repaint. The bubble comes back, now with less history on the wall. Photograph first.
Map the bubble to a fixture or an exterior wall.
A bathroom ceiling after showers is one file. An exterior corner after melt is another.
Do not scrape it all off before anyone sees it.
A dated photo of the bubble is evidence. A smooth new primer is not.
Soft drywall under the bubble moves this to a call.
Finishes failing over a wet cavity are not a cosmetic wait.
Questions people ask
Can I just primer and wait?
You can hide the timeline. If it is wet, you have not fixed it.
Is bubbling always plumbing?
No. Steam, bath fans, and envelope leaks blister paint too.