# CVE-2025-66521: Foxit pdfonline.foxit.com Stored Cross-Site Scripting in Trusted Certificates Feature

> Attackers can inject malicious scripts via certificate names in Foxit PDF Online, leading to script execution when the Trusted Certificates view is loaded.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 19 Dec 2025
- **Updated:** 19 Dec 2025
- **Also known as:** GHSA-8wr8-qf33-p6vc

## What is CVE-2025-66521?

CVE-2025-66521 is a medium-severity cross-site scripting vulnerability in pdfonline.foxit.com, published on 19 Dec 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

A stored cross-site scripting (XSS) vulnerability exists in pdfonline.foxit.com within the Trusted Certificates feature. A crafted payload can be injected as the certificate name, which is later rendered into the DOM without proper sanitization. As a result, the injected script executes each time the Trusted Certificates view is loaded.

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

## Which versions are affected by CVE-2025-66521?

It affects 1 product.


Products: Foxit Pdf Editor Cloud.

## How do I fix CVE-2025-66521?

No fix has been published for CVE-2025-66521 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66521 being exploited?

There is no known exploitation of CVE-2025-66521 in the wild and no public exploit code.

## Other vulnerabilities in pdfonline.foxit.com

- [CVE-2026-1591](https://insights.sbomify.com/CVE-2026-1591/): Stored XSS via Attachments Feature in https://pdfonline.foxit.com/ (medium 6.3)
- [CVE-2026-1592](https://insights.sbomify.com/CVE-2026-1592/): Stored XSS via Create New Layer Field found in Foxit PDF Editor Cloud (medium 6.3)
- [CVE-2025-66500](https://insights.sbomify.com/CVE-2025-66500/): Foxit webplugins.foxit.com Stored Cross-Site Scripting via postMessage Vulnerability (medium 6.3)
- [CVE-2025-66501](https://insights.sbomify.com/CVE-2025-66501/): Foxit pdfonline.foxit.com Stored Cross-Site Scripting in eSign Predefined Text Feature (medium 6.3)
- [CVE-2025-66502](https://insights.sbomify.com/CVE-2025-66502/): Foxit pdfonline.foxit.com Stored Cross-Site Scripting in Page Templates Feature (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66521 and fix it if it is affected.

What it is: CVE-2025-66521 is a medium-severity cross-site scripting vulnerability in pdfonline.foxit.com, published on 19 Dec 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-66521 in the wild and no public exploit code.

Affected product: pdfonline.foxit.com. 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-2025-66521/ (Markdown: https://insights.sbomify.com/CVE-2025-66521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66521
- OSV: https://osv.dev/vulnerability/CVE-2025-66521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66521/
Summaries are generated and may contain mistakes; the official description above is the record.