What do you think WHQL is?

The problem with CrowdStrike's solution is that they got csagent.sys driver signed by WHQL, and the driver will download p-code from the internet and execute it. This allows them to push out changes without waiting for Microsoft approval.

The biggest problem occurs when you don't sanitize your inputs and someone accidentally uploads a blank file padded with zeroes. The driver dereferences a null value, and crashes your system. Hard.