CVE-2026-30977: RenderBlocking has Stored XSS in renderblocking-css with Inline Assets mode

Severity: low (CVSS 2.0 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-10 · updated 2026-06-17
Weakness: CWE-79

Description

RenderBlocking is a MediaWiki extension that allows interface administrators to specify render-blocking CSS and JavaScript. Prior to 0.1.1, there is Stored XSS in renderblocking-css with Inline Assets mode. $wgRenderBlockingInlineAssets = true and editsitecss user rights are required. This vulnerability is fixed in 0.1.1.

Affected products

lihaohong6 RenderBlocking: before 0.1.1

References

https://github.com/lihaohong6/RenderBlocking/commit/096fc47dad9dca153b02cba3db81f412c87fb2be
https://github.com/lihaohong6/RenderBlocking/releases/tag/v0.1.1
https://github.com/lihaohong6/RenderBlocking/security/advisories/GHSA-4h5r-8rjm-496r

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