Steps to Reproduce

1. enable websocket

       	<listener>
       		<listener-class>org.zkoss.zkmax.au.websocket.WebSocketWebAppInit</listener-class>
       	</listener>
   

2. run the zul with 10.0.0.FL.20240215-Eval
3. upload an image

Current Result

The server is temperarily out of service. would you like to try again?
467

Expected Result

the image is showed on the page

Debug Information

• this bug also affects Signature
• using ajax has no such issue

Workaround

• use ajax