Update authority.py

updated the checking on host checking

Author: 4gust

msal/authority.py

@@ -237,9 +237,12 @@ def has_valid_issuer(self):
 
         # Case 3: Regional variant check - O(1) lookup
         # e.g., westus2.login.microsoft.com -> extract "login.microsoft.com"
-        if any(issuer_host.endswith("." + trusted) for trusted in TRUSTED_ISSUER_HOSTS):
-            return True
-        
+        dot_index = issuer_host.find(".")
+        if dot_index > 0:
+            potential_base = issuer_host[dot_index + 1:]
+            if potential_base in TRUSTED_ISSUER_HOSTS and "." not in issuer_host[:dot_index]:
+                return True
+
         # Case 4: Same scheme and host (path can differ)
         if (authority_parsed.scheme == issuer_parsed.scheme and 
             authority_parsed.netloc == issuer_parsed.netloc):