The answer to 'shower overflowing' is that the most common causes are a clogged drain, a problem with the shower diverter valve, or a plumbing vent issue. Symptoms include water spilling out of the shower enclosure, slow draining, or the shower backing up. Solutions can range from simple DIY fixes like using a plunger or drain snake to more complex problems that require a professional plumber.
If the shower is overflowing, the first step is to try to unclog the drain. Use a plunger or drain snake to clear any blockages. If that doesn't work, the issue may be with the shower diverter valve or a problem with the plumbing vent. These types of problems are best handled by a licensed plumber who can properly diagnose and fix the root cause.