# CVE-2021-3977: Cross-site Scripting (XSS) - Stored in invoiceninja/invoiceninja

> Attackers can inject malicious scripts into Invoice Ninja, potentially stealing user sessions or executing code in victim browsers.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-xg6r-5gx4-qxjm

## What is CVE-2021-3977?

CVE-2021-3977 is a medium-severity cross-site scripting vulnerability in invoiceninja/invoiceninja, published on 24 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

invoiceninja is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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

## Which versions are affected by CVE-2021-3977?

2 open source packages ship an affected version, including hillelcoren/invoice-ninja. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hillelcoren/invoice-ninja` | Packagist | All versions | 5.3.35 |
| `hillelcoren/invoice-ninja` | Packagist | All versions | 5.3.35 |

Products: Invoiceninja Invoice Ninja.

## How do I fix CVE-2021-3977?

Upgrade hillelcoren/invoice-ninja to 5.3.35 or later.

## Is CVE-2021-3977 being exploited?

There is no known exploitation of CVE-2021-3977 in the wild and no public exploit code.

## Other vulnerabilities in invoiceninja/invoiceninja

- [CVE-2021-33898](https://insights.sbomify.com/CVE-2021-33898/): Deserialization in n/a (high 8.1)
- [CVE-2026-29925](https://insights.sbomify.com/CVE-2026-29925/): Server-side request forgery in n/a (high 7.7)
- [CVE-2026-33628](https://insights.sbomify.com/CVE-2026-33628/): Invoice Ninja Denylist Bypass may Lead to Stored XSS via Invoice Line Items (medium 5.4)
- [CVE-2026-33742](https://insights.sbomify.com/CVE-2026-33742/): Invoice Ninja has Stored XSS via Markdown HTML Injection in Product Notes (medium 5.4)
- [CVE-2017-1000466](https://insights.sbomify.com/CVE-2017-1000466/): Cross-site scripting in n/a (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3977 and fix it if it is affected.

What it is: CVE-2021-3977 is a medium-severity cross-site scripting vulnerability in invoiceninja/invoiceninja, published on 24 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3977 in the wild and no public exploit code.

Affected packages and fixed versions:
- hillelcoren/invoice-ninja (Packagist): affected all versions; fixed in 5.3.35
- hillelcoren/invoice-ninja (Packagist): affected all versions; fixed in 5.3.35

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-2021-3977/ (Markdown: https://insights.sbomify.com/CVE-2021-3977/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3977
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3977
- OSV: https://osv.dev/vulnerability/CVE-2021-3977

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3977/
Summaries are generated and may contain mistakes; the official description above is the record.