# CVE-2018-1000813: Cross-site scripting in n/a

> An attacker can execute arbitrary JavaScript in the context of a logged-in user's session via malicious class names in Backdrop CMS blocks and layouts.

- **Severity:** Medium 4.8 (`CVSS:3.0/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 20 Dec 2018
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-8wm7-hhmh-8mwj

## What is CVE-2018-1000813?

CVE-2018-1000813 is a medium-severity cross-site scripting vulnerability in n/a, published on 20 Dec 2018. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

Backdrop CMS version 1.11.0 and earlier contains a Cross Site Scripting (XSS) vulnerability in Sanitization of custom class names used on blocks and layouts. that can result in Execution of JavaScript from an unexpected source.. This attack appear to be exploitable via A user must be directed to an affected page while logged in.. This vulnerability appears to have been fixed in 1.11.1 and later.

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

## Which versions are affected by CVE-2018-1000813?

It affects 1 product.


Products: Backdropcms Backdrop Cms.

## How do I fix CVE-2018-1000813?

No fix has been published for CVE-2018-1000813 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-1000813 being exploited?

There is no known exploitation of CVE-2018-1000813 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2019-14771](https://insights.sbomify.com/CVE-2019-14771/): File upload in n/a (critical 9.8)
- [CVE-2022-42092](https://insights.sbomify.com/CVE-2022-42092/): Backdrop CMS Unrestricted File Upload vulnerability (high 7.2)
- [CVE-2019-19902](https://insights.sbomify.com/CVE-2019-19902/): File upload in n/a (high 7.2)
- [CVE-2025-63828](https://insights.sbomify.com/CVE-2025-63828/): Backdrop CMS Host Header Injection vulnerability (medium 6.1)
- [CVE-2025-44141](https://insights.sbomify.com/CVE-2025-44141/): Cross-site scripting in n/a (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-1000813 and fix it if it is affected.

What it is: CVE-2018-1000813 is a medium-severity cross-site scripting vulnerability in n/a, published on 20 Dec 2018. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2018-1000813 in the wild and no public exploit code.

Affected product: n/a. 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-2018-1000813/ (Markdown: https://insights.sbomify.com/CVE-2018-1000813/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-1000813
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-1000813
- OSV: https://osv.dev/vulnerability/CVE-2018-1000813

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-1000813/
Summaries are generated and may contain mistakes; the official description above is the record.