YesWiki Vulnerable to Reflected XSS via Unescaped `id` Parameter in Bazar Widget HTML Attributes

This issue maps to CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').

PoC

1. Set up a vulnerable YesWiki instance with the bundled Bazar extension enabled. This was validated locally on the official doryphore 4.6.5 release.
2. Confirm the minimum access requirements:
   • No account is required.
   • No read or write permission on a specific page is required.
   • No valid existing page tag is required.
   • No valid Bazar form identifier is required.
   • The only observed requirements were that the Bazar widget handler is present and the request includes an id parameter.
3. Request the widget handler with an attribute-breaking payload in id, for example:

http://127.0.0.1:8085/NoSuchPage/widget?id=%22%20onmouseover=%22alert(1)%22%20x=%22

4. Open the URL in a browser as an unauthenticated visitor.
5. Observe that the server returns HTTP 200 and renders the Bazar widget page even though the page tag is arbitrary.
6. Inspect the returned HTML. The response contains attacker-controlled attributes in the widget root element:

<div id="widgetapp" v-cloak
  data-formid="" onmouseover="alert(1)" x=""
  ...
  data-iframeUrl="http://127.0.0.1:8085/NoSuchPage/bazariframe&id=" onmouseover="alert(1)" x=""
>

7. Move the mouse over the widgetapp element or otherwise trigger the injected event handler.
8. The browser executes the injected JavaScript in the YesWiki origin.

Impact

This is a reflected XSS vulnerability in the Bazar widget handler with very low attacker prerequisites.

The practical access model is:

• The attacker only needs to send a crafted public URL.
• The victim does not need to authenticate.
• The attacker does not need edit rights, ownership, or a valid page tag.
• The route only needs to be reachable on a YesWiki instance with Bazar enabled.

An attacker may be able to:

• Execute arbitrary JavaScript in the victim's browser.
• Steal browser-accessible sensitive data.
• Perform actions in the victim's session if the victim is logged in.
• Target public visitors and authenticated users alike because the route is reachable without access-control checks.