Genetic engineering is simply a tool. A particularly malicious individual with an absurd amount of independent resources, ingenuity, and time on eir hands could use it to make something dangerous - but such a comic book supervillain aspirant could be far more effectively evil simply by making a lot of bombs and using them on densely-populated areas.

In the non-comic book world where we live, genetic engineering is done in a veritable regulatory straightjacket. Development of products for human consumption and/or those that will have contact with non-modified organisms must be exhaustively evaluated for risk potential and its expected benefits justified before the research even gets funded, in most if not all cases.

So, no green goo, and no, you should not be afraid. (Interested in the regulatory practices that keep somewhat bullying-inclined corporations such as Monsanto in check, perhaps, but that has little to do with genetic engineering and much to do with corporate politics and asshattery.)