Executive brief
YesWiki, a collaborative wiki platform, contains a security flaw in its Bazar widget component. An attacker can send a specially crafted link to a user that, when clicked, executes malicious code in their web browser. This could allow the attacker to steal sensitive session information or perform unauthorized actions on behalf of the user, regardless of whether the user is logged in.
Technical details
A reflected Cross-Site Scripting (XSS) vulnerability exists in YesWiki's Bazar extension. The vulnerability is located in the `__WidgetHandler.php` and the corresponding template `widget.tpl.html`, where the `id` GET parameter is processed using only `strip_tags()`. Because `strip_tags()` does not escape double quotes, an attacker can break out of HTML attributes like `data-formid` and `data-iframeUrl` to inject arbitrary event handlers (e.g., `onmouseover`). The exploit requires no authentication or valid page permissions and can be triggered by a remote attacker via a crafted URL. The issue is fixed in version 4.6.6.
Affected products
- YesWiki yeswiki < 4.6.6
Timeline
- 2026-06-02: disclosed: Initial disclosure to vendor
- 2026-07-09: advisory: GitHub Advisory published
- 2026-07-09: patched: Fix released in version 4.6.6