# CVE-2021-27910: Stored XSS vulnerability on Bounce Management Callback

> Attackers can inject arbitrary JavaScript via unauthenticated webhook callbacks, leading to code execution and data theft when users view lead details.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/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:** 30 Aug 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-86pv-95mj-7w5f

## What is CVE-2021-27910?

CVE-2021-27910 is a high-severity cross-site scripting vulnerability in Mautic, published on 30 Aug 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

Insufficient sanitization / filtering allows for arbitrary JavaScript Injection in Mautic using the bounce management callback function. The values submitted in the "error" and "error_related_to" parameters of the POST request of the bounce management callback will be permanently stored and executed once the details page of an affected lead is opened by a Mautic user. An attacker with access to the bounce management callback function (identified with the Mailjet webhook, but it is assumed this will work uniformly across all kinds of webhooks) can inject arbitrary JavaScript Code into the "error" and "error_related_to" parameters of the POST request (POST /mailer/<product / webhook>/callback). It is noted that there is no authentication needed to access this function. The JavaScript Code is stored permanently in the web application and executed every time an authenticated user views the details page of a single contact / lead in Mautic. This means, arbitrary code can be executed to, e.g., steal or tamper with information.

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

## Which versions are affected by CVE-2021-27910?

4 open source packages ship an affected version, including mautic/core. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mautic/core` | Packagist | All versions | 3.3.4 |
| `mautic/core` | Packagist | All versions | 3.3.4 |
| `mautic/core` | Packagist | From 4.0.0-alpha1 | 4.0.0 |
| `mautic/core` | Packagist | From 4.0.0-alpha1 | 4.0.0 |

Products: Acquia Mautic.

## How do I fix CVE-2021-27910?

Upgrade mautic/core to a fixed version for your release line: 3.3.4 or 4.0.0.

## Is CVE-2021-27910 being exploited?

There is no known exploitation of CVE-2021-27910 in the wild and no public exploit code.

## Other vulnerabilities in Mautic

- [CVE-2022-25772](https://insights.sbomify.com/CVE-2022-25772/): Cross-site Scripting vulnerability in Mautic's tracking pixel functionality (critical 9.6)
- [CVE-2020-35125](https://insights.sbomify.com/CVE-2020-35125/): Mautic is vulnerable to XSS vulnerability (critical 9.6)
- [CVE-2020-35124](https://insights.sbomify.com/CVE-2020-35124/): XSS vulnerability leveraged through referrers could allow un-authorized admin access in Mautic (critical 9.6)
- [CVE-2024-47051](https://insights.sbomify.com/CVE-2024-47051/): Remote Code Execution & File Deletion in Asset Uploads (critical 9.1)
- [CVE-2020-35128](https://insights.sbomify.com/CVE-2020-35128/): Mautic stored Cross-site Scripting (XSS) (critical 9.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27910 and fix it if it is affected.

What it is: CVE-2021-27910 is a high-severity cross-site scripting vulnerability in Mautic, published on 30 Aug 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-2021-27910 in the wild and no public exploit code.

Affected packages and fixed versions:
- mautic/core (Packagist): affected all versions; fixed in 3.3.4
- mautic/core (Packagist): affected all versions; fixed in 3.3.4
- mautic/core (Packagist): affected from 4.0.0-alpha1; fixed in 4.0.0
- mautic/core (Packagist): affected from 4.0.0-alpha1; fixed in 4.0.0

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-2021-27910/ (Markdown: https://insights.sbomify.com/CVE-2021-27910/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27910
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27910
- OSV: https://osv.dev/vulnerability/CVE-2021-27910

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27910/
Summaries are generated and may contain mistakes; the official description above is the record.