Product/(s) of the following reaction
If you're sure that the initial formula is $\ce{H3COOCH3}$ (and that's a big if), then I disagree with Richard's answer in comments. $\ce{H3COOCH3}$ is dimethyl peroxide. While peroxides are not the most stable of molecules, and decompose rapidly (often by oxidizing other compounds), they do not spontaneously transform in acid conditions.

If the formula were $\ce{H3C–COOCH3}$ (note the added C), then yes, it's be acid-catalysed ester hydrolysis.