CVE-2026-77610: Semantic MediaWiki has a query debug output XSS (`DebugFormatter`)

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-18 · updated 2026-09-24
Weakness: CWE-79

Description

Semantic MediaWiki is a free, open-source extension to MediaWiki that lets users store and query data within the wiki's pages. Prior to version 7.2.0, query debug output (`format=debug`, or the `debug` request parameter on `Special:Ask`) is assembled by `SMW\Query\DebugFormatter` and emitted as raw HTML. Several of its sinks apply no output-context encoding, so attacker-controlled query input is reflected into the page without escaping. On `Special:Ask` the resulting string is concatenated into the page and sent through `OutputPage::addHTML`, never through the MediaWiki parser or Sanitizer. No special user right is required; an anonymous request suffices. This is a reflected XSS: the payload is taken from the request and echoed in the same response. Exploitation requires the query condition to target a text/blob-typed property (whose value is re-serialized verbatim); the predefined `_txt` properties (`Text`, etc.) that ship on every install satisfy this, so no attacker-created content is needed. Version 7.2.0 patches the issue.

Affected products

SemanticMediaWiki: before 7.2.0

References

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