fix(api): issue2551384. Verify REST authorization earlier To reduce the ability of bad actors to spam (DOS) the REST endpoint with bad data and generate logs meant for debugging, modify the flow in client.py's REST handler to verify authorization earlier. If the anonymous user is allowed to use REST, this won't make a difference for a DOS attempt. The templates don't enable REST for the anonymous user by default. Most admins don't change this. The validation order for REST requests has been changed. CORS identfied an handled User authorization to use REST (return 403 on failure) REST request validated (Origin header valid etc.) (return 400 for bad request) Incorrectly formatted CORS preflight requests (e.g. missing Origin header) that are not recogized as a CORS request can now return HTTP status 403 as well as status 400 (when anonymous is allowed access). Note all CORS preflights are sent without authentication so appear as anonymous requests. The tests were updated to compensate, but it is not obvious to me from specs what the proper evaulation order/return codes should be for this case. Both 403/400 are failures and cause CORS to fail so there should be no difference but...

--- a/doc/upgrading.txt	Wed Jan 08 11:39:54 2025 -0500
+++ b/doc/upgrading.txt	Thu Jan 09 09:30:08 2025 -0500
@@ -224,6 +224,17 @@
 
 .. _defusedxml: https://pypi.org/project/defusedxml/
 
+Change in REST response for invalid CORS requests (info)
+--------------------------------------------------------
+
+CORS_ preflight requests that are missing required headers can
+now result in either a 403 or 400 error code. If you permit
+anonymous users to access the REST interface, a 400 error may
+still occur. Previously, only a 400 error was given. This change
+is not expected to create issues since the client will recognize
+both codes it as an error response, and the CORS request will
+still fail.
+
 More secure session cookie handling (info)
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