[Bug] AcquireTokenSilent redirects to fabrikamb2c.onmicrosoft.com in B2C web app / web API sample

[MINDoSOFT]

Logs and Network traces

Which Version of MSAL are you using ?
MSAL 4.26.0

Platform
net451

What authentication flow has the issue?

• Web App
  • Authorization code
  • OBO

Is this a new or existing app?
This is a sample web application part of Azure-Samples.

Repro

Please run the sample application, and login.
Go to the tasks page.
Wait for an hour, for the access token to expire.
Navigate to the tasks page.
You will be redirected to the

/fabrikamb2c.onmicrosoft.com/b2c_1_susi/oauth2/v2.0/authorize?client_id=fdb91ff5-5ce6-41f3-bdbd-8267c817015d&redirect_uri=https%3A%2F%2Flocalhost%3A44316%2F&response_mode=form_post&response_type=code%20id_token&scope=openid%20profile%20offline_access%20https%3A%2F%2Ffabrikamb2c.onmicrosoft.com%2Ftasks%2Fread%20https%3A%2F%2Ffabrikamb2c.onmicrosoft.com%2Ftasks%2Fwrite&state=OpenIdConnect.AuthenticationProperties%3DuSXsJe7x41d0OCr2_UwJI4xEq2ygRjQiJyagTH6fBI8OOQ-SPz1xCrLjXL9QZigI1d1ppXnIIpy5solLdEZWozRI-Yf4gaMgZNQM6B6OU58AKMMK3PGfz1-783GZc9mJSOO_MMZjxFRHgDVGhUB1Lb_JZbP-DbJhHebVouqrdCpo-SW1P9SLbjANG-6AtWWzt_lFmRFxnzZDsWl0lxl2Zg&nonce=637509045992290365.YmYxZGQwNTAtZTBhZS00ODg4LWFjNTktZWM3NTljZDc2NjFiZjUwNGFlZmQtNjIzNy00MmIwLTg1ZDYtNzAwYjNlMWE1NjAy&x-client-SKU=ID_NET451&x-client-ver=5.4.0.0

page.

Expected behavior
Since I have a refresh token which is valid for 14 days, I was expecting AcquireTokenSilent to request a new access token without redirecting anywhere.

Actual behavior
A redirection to /fabrikamb2c.onmicrosoft.com/b2c_1_susi/oauth2/v2.0/authorize occurs (see detailed url above), to retrieve a totally new access token and refresh token.

Possible Solution

Additional context/ Logs / Screenshots
I've also created an issue on the sample application.

Thank you very much for your time and effort,
Sergios.

[jmprieur]

This is an issue with the sample, @MINDoSOFT. I need to take the time to look at it.
Do you really need to use ASP.NET ? can't you move to ASP.NET Core? In ASP.NET Core everthing is magically handled for your by Microsoft.Identity.Web. See https://github.com/Azure-Samples/active-directory-aspnetcore-webapp-openidconnect-v2/tree/master/4-WebApp-your-API/4-2-B2C

[MINDoSOFT]

Thank you for your prompt reply.

Unfortunately moving to ASP.NET Core is not possible. Because we are integrating Azure B2C with an existing project which uses .NET Framework 4.8 and Web Forms.

[bgavrilMS]

Please open an issue on the sample if it hasn't been fixed.