IFrame issues after Microsoft changed default settings to SameSite cookie attribute

Chrome will be automatically changing session cookies with SameSite="None" to SameSite="Lax".

Microsoft is preemptively addressing this with the following update.
https://support.microsoft.com/en-us/help/4524420/kb4524420

Due to this, Microsoft ASP.NET will now emit a SameSite cookie header when HttpCookie.SameSite value as "None"

This caused an issue with a client's IFrame which was loading a page from their largest customer's site.

Set the cookieSameSite= "None" in the session state tag to avoid this issue.

<sessionState cookieSameSite="None" cookieless="false" timeout="360">
</sessionState>

<%= heading %>