Added error message

Author: Karuna-Mendix

content/en/docs/appstore/use-content/platform-supported-content/modules/SAML/_index.md

@@ -560,6 +560,7 @@ When enabling the log node SSO to show trace messages, you can find detailed inf
 * **“MSIS7046: The SAML protocol parameter ‘RelayState’ was not found or not valid.”** – This error can be shown on the ADFS server, most likely when you are using Mac OSX and a Safari browser. Setting the `BindingURI_Redirect` constant to true might help resolve the issue. By default, Mendix favors the `Post` binding, as the maximum size exceeds that of a `Redirect` binding due to its use of cookies and post information instead of URL parameters. The size can be a factor when using encryption.
 * **"Unable to validate Response, see SAMLRequest overview for detailed response. Error: An error occurred while committing user: p:'johndoe@company.com'/u:'JoHnDoE@CoMpAnY.CoM'"** – All user names passing through the SAML module are converted to lower-case, so make sure all the existing user names and new user names are also converted to lower-case. This is because certain systems are not case-sensitive (for example, Active Directory).
 * **“Could not create a session for the provided user principal.”** – This error can be shown if the IdP configuration does not contain any application attributes for the entity where the user (and user principal) is to be found (and stored).
+* **"WARN org.apache.xml.security.signature.XMLSignature - Signature verification failed"** – The signature validation process fails due to multiple certificates in the IdP metadata used for SSO. As the service provider attempts to verify the signature against each certificate, it generates 'Signature verification failed' warnings for incorrect matches.
 
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