# CVE-2019-11720: Cross-site scripting in Firefox

> Attackers can bypass XSS filters by using specific Unicode characters treated as whitespace, allowing malicious code execution in Firefox.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A: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:** Yes
- **Published:** 23 Jul 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-c4xq-jjr6-4q6x, UBUNTU-CVE-2019-11720

## What is CVE-2019-11720?

CVE-2019-11720 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 23 Jul 2019. 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

Some unicode characters are incorrectly treated as whitespace during the parsing of web content instead of triggering parsing errors. This allows malicious code to then be processed, evading cross-site scripting (XSS) filtering. This vulnerability affects Firefox < 68.

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

## Which versions are affected by CVE-2019-11720?

It affects 2 products.


Products: Mozilla Firefox, Opensuse Leap.

## How do I fix CVE-2019-11720?

Upgrade to a fixed version.

## Is CVE-2019-11720 being exploited?

There is no known exploitation of CVE-2019-11720 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Firefox

- [CVE-2019-11708](https://insights.sbomify.com/CVE-2019-11708/): Mozilla Firefox and Thunderbird Sandbox Escape (critical 10.0, exploited in the wild)
- [CVE-2010-3765](https://insights.sbomify.com/CVE-2010-3765/): Mozilla Multiple Products Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-26486](https://insights.sbomify.com/CVE-2022-26486/): Mozilla Firefox Use-After-Free (critical 9.6, exploited in the wild)
- [CVE-2022-26485](https://insights.sbomify.com/CVE-2022-26485/): Mozilla Firefox Use-After-Free (high 8.8, exploited in the wild)
- [CVE-2019-11707](https://insights.sbomify.com/CVE-2019-11707/): Mozilla Firefox and Thunderbird Type Confusion (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-11720 and fix it if it is affected.

What it is: CVE-2019-11720 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 23 Jul 2019. 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-2019-11720 in the wild and no public exploit code.

Affected product: Mozilla Firefox. 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-2019-11720/ (Markdown: https://insights.sbomify.com/CVE-2019-11720/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-11720
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-11720
- OSV: https://osv.dev/vulnerability/CVE-2019-11720

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-11720/
Summaries are generated and may contain mistakes; the official description above is the record.