Hello @Ko Ko Tun ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand that you are getting an "Access denied with code 403 (phase 2). Match of \"eq 0\" against \"MULTIPART_UNMATCHED_BOUNDARY\" required" error in Application gateway WAF logs with ruleId_s = 200004 when you try to upload screenshots to your server.
I checked with the Application gateway WAF Product Group team and below is their update:
Yes, this is a known issue, and we are in process of rolling out a fix. Workaround to disable this rule is reasonable for time being.
This bug/known issue is being tracked internally and a fix will be rolled out soon.
Kindly let us know if the above helps or you need further assistance on this issue.
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