# CVE-2026-47733: Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images

> Authenticated users can inject JavaScript via markdown images, potentially executing code in viewers' sessions.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 24 Jun 2026
- **Updated:** 25 Jun 2026
- **Also known as:** GHSA-vvrf-fq54-q4pr

## What is CVE-2026-47733?

CVE-2026-47733 is a medium-severity cross-site scripting vulnerability in RocketChat Rocket.Chat, published on 24 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.0, the ImageElement component in packages/gazzodown renders user-controlled src values directly into <a href> and <img src> attributes without protocol sanitization. Unlike the analogous LinkSpan component — which uses sanitizeUrl to block javascript:, data:, and vbscript: protocols — ImageElement passes the raw URL through unchanged. An authenticated user can post a markdown image with a javascript: URL that, if clicked on an older browser, would execute arbitrary JavaScript in the viewer's session. This vulnerability is fixed in 8.5.0.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-47733?


## How do I fix CVE-2026-47733?

No fix has been published for CVE-2026-47733 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-47733 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47733 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47733 and fix it if it is affected.

What it is: CVE-2026-47733 is a medium-severity cross-site scripting vulnerability in RocketChat Rocket.Chat, published on 24 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47733 exists.

Affected product: RocketChat Rocket.Chat. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47733/ (Markdown: https://insights.sbomify.com/CVE-2026-47733/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47733
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47733
- OSV: https://osv.dev/vulnerability/CVE-2026-47733

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47733/
Summaries are generated and may contain mistakes; the official description above is the record.