SSO fails for some existing users

[petrm]

Hello,

after upgrading to 2026.5.0 and the matching SSO tag, I am facing issues for (some) existing SSO users.

The error is coming from

sso/challenge.js

Lines 236 to 239 in 7c44ebb

	if (userData?.block !== publicKey) {
	w.abort();
	return void cb('SSO_INVALID_BLOCK');
	}

On the client I see 500 for the respective api call in the console, no details.

I worked around the issue by commenting out the block of code in question, it seems to be new in this release.

Additionally, every time a user tries to log in (clicks the login button on the front page), the following error is shown in the browser console:
/api/auth/ 500 (Internal Server Error)
The response content is
{"error":"Execution error","errorCode":"E_REQ_WRITE"}

The UI shows a red "Error" banner. Refreshing the page results in the same error, the user has to refresh the page without cache and is then correctly redirected to the SSO login page.

Not sure if the two issues are related.

[ykonyshev]

I have also encountered the second issue with the 500 response from /api/auth and the "Error" banner on the client and the "E_REQ_WRITE" error code showing up in the logs. I am also on 2026.5.0. The error seems to be caused by this line:

sso/challenge.js

Line 46 in 7c44ebb

if (err) { return void cb("E_REQ_WRITE"); }

Not sure about the mechanics of the authentication flow and the precise reason why the error occurs, but I thought it would worth mentioning that this is not an isolated case... And yes, the Ctrl + F5 refresh fixes it.