Again, it's not just malicious updates. Normal updates can also introduce security vulnerabilities. For example, I have a dependency at v1.0 and v1.0.1 introduces a security bug unintentionally. It is eventually fixed in v1.1. If I wait to update until v1.1, then I am not vulnerable to that bug whereas an automatic update to v1.0.1 would be vulnerable. My point is that in expectation, updating your dependency could be just as likely to remove a security vulnerability as it is to add one.