Escape special characters in Basic Auth?

[Joan_Davis]

I’ve created a task that calls a webhook. The web service uses basic auth. I set the header to something like the base64 encoded value below:

Authorization: Basic cm9tZXRpvU26Om51cHRpYWxz==

AppSheet gives this error:

Now, if I change my credentials for the web service to something that produces an encoded value without the special characters (==), AppSheet is happy…and the POST request works.

What is the proper way to include special characters in the auth header?

Thank you.