Merge pull request #294481 from Miskatonic-Electronic/patch-50

Update custom-waf-rules-overview.md

Author: prmerger-automator[bot]

articles/web-application-firewall/ag/custom-waf-rules-overview.md

@@ -162,6 +162,9 @@ A list of strings with names of transformations to do before the match is attemp
 
 List of values to match against, which can be thought of as being *OR*'ed. For example, it could be IP addresses or other strings. The value format depends on the previous operator.
 
+> [!NOTE]
+> If your WAF is running Core Rule Set (CRS) 3.1, or any other earlier CRS version, the match value only allows letters, numbers and punctuation marks. Quotation marks `"`, `'` and spaces are not supported.
+
 Supported HTTP request method values include:
 - GET
 - HEAD