# CVE-2026-78187: Piwigo Public Authentication cross site scripting

> Remote attackers can inject malicious scripts via the lang parameter in Piwigo's public authentication page, potentially compromising user sessions.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P`)
- **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:** No
- **Published:** 24 Aug 2026
- **Updated:** 24 Aug 2026
- **Also known as:** GHSA-p4vh-hfqq-9prq, GHSA-rr39-mf4j-6594

## What is CVE-2026-78187?

CVE-2026-78187 is a low-severity cross-site scripting vulnerability in Piwigo, published on 24 Aug 2026. 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

A vulnerability has been found in Piwigo 16.3.0. This impacts an unknown function of the component Public Authentication Page. Such manipulation of the argument lang leads to cross site scripting. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is said to be difficult. The exploit has been disclosed to the public and may be used. Upgrading to version 16.4.0 will fix this issue. The name of the patch is 5277a7dee4b8f1a174f1d69e1e2a4e1c82a3fc9e. It is recommended to upgrade the affected component.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-78187?


## How do I fix CVE-2026-78187?

No fix has been published for CVE-2026-78187 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-78187 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-78187 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-78187 and fix it if it is affected.

What it is: CVE-2026-78187 is a low-severity cross-site scripting vulnerability in Piwigo, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-78187 exists.

Affected product: Piwigo. 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-2026-78187/ (Markdown: https://insights.sbomify.com/CVE-2026-78187/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-78187
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-78187
- OSV: https://osv.dev/vulnerability/CVE-2026-78187

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-78187/
Summaries are generated and may contain mistakes; the official description above is the record.