Why must the base64-encoded payload be URL-encoded when sending to the memory loading backdoor via C#?

The base64 string often contains the `=` character, which in POST data with `Content-Type: application/x-www-form-urlencoded` is interpreted as a key-value separator. Therefore, the `=` must be URL-encoded to `%3d` to avoid breaking the parameter structure. The C# code uses `HttpUtility.UrlEncode` to handle this encoding automatically. Proper encoding is critical for successful payload delivery, as highlighted in the original Penetration Basics - Implementation of Exchange One-Liner Backdoor.