Chrome will be automatically changing session cookies with SameSite="None" to SameSite="Lax".
Microsoft is preemptively addressing this with the following update.
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">
Taken from this post