GitHub OAuth provider no longer works. Was there some recent change by GitHub?

Provider type

GitHub

Environment

  System:
    OS: Windows 10 10.0.19045
    CPU: (8) x64 Intel(R) Xeon(R) CPU E31245 @ 3.30GHz
    Memory: 4.06 GB / 15.96 GB
  Binaries:
    Node: 22.17.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.22 - C:\Users\me\AppData\Roaming\npm\yarn.CMD
    npm: 10.9.2 - C:\Program Files\nodejs\npm.CMD
    bun: 1.2.18 - C:\Users\me\AppData\Roaming\npm\bun.CMD
  Browsers:
    Edge: Chromium (140.0.3485.54)
    Firefox: 149.0.2 - C:\Program Files\Mozilla Firefox\firefox.exe
    Firefox Developer Edition: 150.0 - C:\Program Files\Firefox Developer Edition\firefox.exe
    Internet Explorer: 11.0.19041.5794

Reproduction URL

https://github.com/dataspecer/dataspecer/tree/git-integration

Describe the issue

The issue is that when I try to sign-in using GitHub I get an server error seen below. Both when using my application and the official deployed example. I am 100% sure that my application worked a month ago and almost 100% sure that it did work 4 days ago. I also tried going back to older commits with the same result. Therefore, the issue should not be caused by me.

The sign-in results in the following image:

When running locally with debug option on I get the following error:

[auth][debug]: callback route error details {
  "method": "GET",
  "query": {
    "code": "xxxxxxxxxxxxxe0b2b",
    "iss": "https://github.com/login/oauth"
  }
}
[auth][error] CallbackRouteError: Read more at https://errors.authjs.dev#callbackrouteerror
[auth][cause]: OperationProcessingError: unexpected "iss" (issuer) response parameter value
    at OPE (C:\Users\me\my-oauth\node_modules\oauth4webapi\src\index.ts:1044:10)
    at Module.validateAuthResponse (C:\Users\me\my-oauth\node_modules\oauth4webapi\src\index.ts:5586:11)
    at handleOAuth (file:///C:/Users/me/my-oauth/node_modules/@auth/core/lib/actions/callback/oauth/callback.js:93:29)
    at async Module.callback (file:///C:/Users/me/my-oauth/node_modules/@auth/core/lib/actions/callback/index.js:37:41)
    at async AuthInternal (file:///C:/Users/me/my-oauth/node_modules/@auth/core/lib/index.js:29:24)
    at async Auth (file:///C:/Users/me/my-oauth/node_modules/@auth/core/index.js:111:34)
    at async file:///C:/Users/me/my-oauth/node_modules/@auth/express/index.js:151:45
[auth][details]: {
  "expected": "https://authjs.dev",
  "parameters": {},
  "provider": "github"
}

How to reproduce

Try signing in to the example URL using GitHub.

Expected behavior

I should be signed in with no issues. Any quick help would be greatly appreciated, since I have a project deadline in a couple of days.

Reproduce the failure at the linked example URL, then start with the callback trace in @auth/core/lib/actions/callback/oauth/callback.js and oauth4webapi's validateAuthResponse. Compare the returned GitHub issuer with the expected value shown in the debug details. Done means GitHub sign-in completes without the issuer or callback error.