We're trying to load an external url in our custom tab. The login page for this domain appears successfully, however when we proceed and try to sign in it stays on the page and does not redirect user to home screen. Here are some observations:
When the same URL is loaded in teams "Website" tab then everything works as expected.
Teams "Website" tab loads the url as it is i.e. WITHOUT iFrame and the custom tab loads the url within an iFrame.
In console window on login inside iFrame I can see cookies related issue which is something like:
"Because a cookie’s SameSite attribute was not set or is invalid, it defaults to SameSite=Lax, which prevents the cookie from being set in a cross-site context. This behavior protects user data from accidentally leaking to third parties and cross-site request forgery. Resolve this issue by updating the attributes of the cookie: Specify SameSite=None and Secure if the cookie is intended to be set in cross-site contexts. Note that only cookies sent over HTTPS may use the Secure attribute. Specify SameSite=Strict or SameSite=Lax if the cookie should not be set by cross-site requests."
Any help or hint would be greatly appreciated.