To fix bubbling paint caused by applying latex paint over oil-based paint in a bathroom, you’ll need to follow these steps:

1. **Prepare the Area:** Ensure proper ventilation in the bathroom by opening windows or using a fan. Lay down a drop cloth to protect the floor from any paint drips.

2. **Remove the Bubbling Paint:** Use a putty knife or scraper to gently remove the bubbling latex paint. Sand the area lightly to create a smooth surface for repainting.

3. **Prime the Surface:** Apply a bonding primer that is specifically designed to cover oil-based surfaces. This will create a suitable base for the new paint to adhere to.

4. **Repaint:** Once the primer has dried according to the manufacturer’s instructions, paint over the primed area with a high-quality latex paint. Make sure to use a paint suitable for bathrooms to withstand moisture and humidity.

5. **Apply Multiple Coats:** Depending on the color and coverage, you may need to apply multiple coats of paint. Allow each coat to dry completely before applying the next one.

6. **Maintain Proper Ventilation:** To prevent similar issues in the future, ensure that the bathroom has adequate ventilation to allow moisture to escape, reducing the likelihood of paint bubbling.