The Short Grass texture is randomly offset on all blocks. While this is intended behavior, this can cause the texture to clip through blocks, and that is not something that short grass should do. To replicate this, get 2 trapdoors and some short grass. Place the grass, and flip up the trapdoors. If the offset is severe enough on that block, you may see some of the short grass's texture. This is usually worst on the corner of blocks, shown here:

This is the worst that I have seen.

A final note:

This is a very minor bug that doesn't affect gameplay at all. It is just one random thing that I saw one day, so I wouldn't be surprised if it won't be fixed.