# CVE-2026-66824: Stored Cross-Site Scripting via Unsafe Capture Tree JSON Embedding

> Stored XSS in lookyloo allows attackers to execute arbitrary scripts in victims' browsers via crafted capture tree data, leading to session hijacking or data manipulation.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 27 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-vjmw-phg6-9f2x

## What is CVE-2026-66824?

CVE-2026-66824 is a critical cross-site scripting vulnerability in lookyloo, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A stored cross-site scripting vulnerability existed in the capture tree visualization page. The application embedded the serialized capture tree directly into an inline JavaScript block using the Jinja safe filter.

Because the tree data can contain values derived from captured and potentially attacker-controlled web content, a specially crafted value could prematurely terminate the surrounding <script> element and inject arbitrary HTML or JavaScript. The malicious code would execute in the browser of a user viewing the affected capture tree.

Successful exploitation could allow an attacker to perform actions using the victim’s authenticated session, access information available to the victim, or modify application data within the permissions of the affected user.

The patch removes the JSON data from the HTML document and retrieves it through a dedicated API endpoint. The client then processes the response using response.json(), preventing capture data from being interpreted as executable content within the original page’s HTML or JavaScript context.

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

## Which versions are affected by CVE-2026-66824?


## How do I fix CVE-2026-66824?

No fix has been published for CVE-2026-66824 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66824 being exploited?

There is no known exploitation of CVE-2026-66824 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66824 and fix it if it is affected.

What it is: CVE-2026-66824 is a critical cross-site scripting vulnerability in lookyloo, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-66824 in the wild and no public exploit code.

Affected product: lookyloo. 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-2026-66824/ (Markdown: https://insights.sbomify.com/CVE-2026-66824/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66824
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66824
- OSV: https://osv.dev/vulnerability/CVE-2026-66824

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66824/
Summaries are generated and may contain mistakes; the official description above is the record.