Sign-out is limited to custom policy

Author: yoelhor

articles/active-directory-b2c/session-overview.md

@@ -95,13 +95,17 @@ Upon a sign-out request, Azure AD B2C:
    - SAML - If the identity provider metadata contains the `SingleLogoutService` location.
 1. Optionally, signs-out from other applications. For more information, see the [Single sign-out](#single-sign-out) section.
 
-> [!NOTE]
-> The sign-out clears the user's single sign-on state with Azure AD B2C, but it might not sign the user out of their social identity provider session. If the user selects the same identity provider during a subsequent sign-in, they might reauthenticate without entering their credentials. If a user wants to sign out of the application, it doesn't necessarily mean they want to sign out of their Facebook account. However, if local accounts are used, the user's session ends properly.
+The sign-out clears the user's single sign-on state with Azure AD B2C, but it might not sign the user out of their social identity provider session. If the user selects the same identity provider during a subsequent sign-in, they might reauthenticate without entering their credentials. If a user wants to sign out of the application, it doesn't necessarily mean they want to sign out of their Facebook account. However, if local accounts are used, the user's session ends properly.
+
+### Single sign-out 
 
-### Single sign-out
+
+> [!NOTE]
+> This feature is limited to [custom policy](custom-policy-overview.md).
 
 When you redirect the user to the Azure AD B2C sign-out endpoint (for both OAuth2 and SAML protocols), Azure AD B2C clears the user's session from the browser. However, the user might still be signed in to other applications that use Azure AD B2C for authentication. To enable those applications to sign the user out simultaneously, Azure AD B2C sends an HTTP GET request to the registered `LogoutUrl` of all the applications that the user is currently signed in to.
 
+
 Applications must respond to this request by clearing any session that identifies the user and returning a `200` response. If you want to support single sign-out in your application, you must implement a `LogoutUrl` in your application's code. 
 
 ## Next steps