Cross-site XHR with headers set fails to authenticate with proxy

Is there an existing issue for this?

[X] I have searched both open/closed issues, no issue already exists.

CefSharp Version

125.0.210

Operating System

Windows 11

Architecture

x64

.Net Version

4.701

Implementation

WinForms

Reproduction Steps

Set windows up with system proxy configured to be an authenticating proxy using NTLM authentication

Add minimum CEF component Load Page A (doesn't matter what provided page B accepts it as an origin for cross-site XHR) Show dev tools In Dev console do eg:

var oReq = new XMLHttpRequest();
oReq.onload = () => { console.log(oReq.responseText) }
oReq.open("GET","https://httpbin.org/get");
oReq.setRequestHeader("afoo","bar")
oReq.send()

Expected behavior

The the above javascript completes without error and logs the response

Actual behavior

When the header is specified then the XHR fails with ERR:FAILED If you remove the line to add the header then the request succeeds

Regression?

No response

Known Workarounds

No response

Does this problem also occur in the CEF Sample Application

Yes - WinForms

cefsharp / CefSharp