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GHSA-hg8h-557g-q8pp

HighCVSS 8.6 / 10
Published Sep 18, 2026·Last modified Sep 18, 2026
Affected Components(1)
Packagist logomediawiki/semantic-media-wiki
3.1.0 – 7.0.0
Description

Summary

The SemanticMediaWiki extension inserts the unsanitized value of a data attribute into the DOM as HTML, allowing for stored XSS through wikitext.

Details

In ext.smw.js, the data-subtab attribute of all elements with the smw-subtab class is parsed as JSON and appended to the innerHTML of the element: https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/62f1fa765b626e21d88999b97a3e8029db9fd385/res/smw/ext.smw.js#L37-L42 However, most data attributes (except for reserved ones) like data-subtab can be used in wikitext. Therefore, it is possible to insert arbitrary HTML and JS through wikitext. The decoded (" will turn to &quot;, but it will be decoded when it is retrieved through .dataset) value of the data-subtab attribute in the payload is "<img src='' onerror=alert(1)>". This is valid JSON and returns a string with <img src='' onerror=alert(1)> when being decoded.

PoC

  1. Create a page with the following contents:
{{#tag:div|
|class=smw-subtab
|data-subtab=""<img src='' onerror=alert(1)>""
}}
  1. Visit the page
<img width="991" height="465" alt="image" src="https://github.com/user-attachments/assets/5d28d852-72d6-41dc-a59a-faac1610015f" /> <img width="497" height="69" alt="image" src="https://github.com/user-attachments/assets/02309390-0b40-46d9-b690-de8cd25dba59" />

Impact

Arbitrary HTML can be inserted into the DOM by any user with the edit right, allowing for JavaScript to be executed.

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Risk Scores
Base Score
8.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
7.9

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.29%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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