# CVE-2021-43544: Cross-site scripting in Firefox

> Firefox for Android users are vulnerable to XSS and spoofing when URLs from SEND intents are unintentionally loaded in the address bar.

- **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:** 8 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-7w2r-8gq9-28xx

## What is CVE-2021-43544?

CVE-2021-43544 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 8 Dec 2021. 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

When receiving a URL through a SEND intent, Firefox would have searched for the text, but subsequent usages of the address bar might have caused the URL to load unintentionally, which could lead to XSS and spoofing attacks. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 95.

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

## Which versions are affected by CVE-2021-43544?

It affects 1 product.


Products: Mozilla Firefox.

## How do I fix CVE-2021-43544?

Upgrade to a fixed version.

## Is CVE-2021-43544 being exploited?

There is no known exploitation of CVE-2021-43544 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-2021-43544 and fix it if it is affected.

What it is: CVE-2021-43544 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 8 Dec 2021. 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-2021-43544 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-2021-43544/ (Markdown: https://insights.sbomify.com/CVE-2021-43544/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43544
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43544
- OSV: https://osv.dev/vulnerability/CVE-2021-43544

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43544/
Summaries are generated and may contain mistakes; the official description above is the record.