Yes, security vulnerabilities are about the only case when you have to react. The kinds of libraries that can introduce security vulnerabilities (crypto, networ

Yes, security vulnerabilities are about the only case when you have to react. The kinds of libraries that can introduce security vulnerabilities (crypto, networking, etc) are hard to write by yourself. If you do happen to write that code by yourself -- to minimize dependencies -- chances are it's full of security holes anyway. Security is hard!