Any code modification is a potential security issue. There is nothing special about dynamic class redefinition in this regard.

I use it for development and deployment. I can deploy new code without having to take my application down. In fact, not only do all my existing instances get updated, but I also use an ORM [1] that automatically updates my database tables too.

[1] https://github.com/rongarret/ergolib/blob/master/layer1/sql....