Added link in AesManaged to article warning of timing vulnerabilities… (#2609)

* Added link in AesManaged to article warning of timing vulnerabilities with CBC-mode symmetric decryption using padding.

* Update xml/System.Security.Cryptography/AesManaged.xml

Co-Authored-By: Maira Wenzel <[email protected]>

Co-authored-by: Maira Wenzel <[email protected]>

Author: samrueby

xml/System.Security.Cryptography/AesManaged.xml

@@ -42,7 +42,8 @@
 > [!NOTE]
 >  If the Windows security policy setting for Federal Information Processing Standards (FIPS)-compliant algorithms is enabled, using this algorithm throws a <xref:System.Security.Cryptography.CryptographicException>.  
   
-   
+> [!NOTE]
+> Microsoft believes that it's no longer safe to decrypt data encrypted with the Cipher-Block-Chaining (CBC) mode of symmetric encryption (which is the default value of the <xref:System.Security.Cryptography.AesManaged.Mode> property) when verifiable padding has been applied without first ensuring the integrity of the ciphertext, except for very specific circumstances. For more information, see [Timing vulnerabilities with CBC-mode symmetric decryption using padding](~/docs/standard/security/vulnerabilities-cbc-mode.md).
   
 ## Examples  
  The following example demonstrates how to encrypt and decrypt sample data using the <xref:System.Security.Cryptography.AesManaged> class.