5c5e04ea-21ce-41b1-956a-43ee07200xxx is not a valid GUID (x is not allowed as character), but isGuid() still returns true. Using this regex to test should fix the problem: `^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}$`;
5c5e04ea-21ce-41b1-956a-43ee07200xxx is not a valid GUID (x is not allowed as character), but isGuid() still returns true.
Using this regex to test should fix the problem:
^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}$;