---
title: "CVE-2026-107845: Contao: Cross-site scripting in the comments bundle"
url: https://erroneo.us/security/cve/CVE-2026-107845/
description: "CVE-2026-107845 (contao/comments-bundle (Composer (PHP))): Contao is an Open Source CMS. From version 4.0.0 until 5.3.50 and 5.7.12, an unauthenticated…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-09
date_modified: 2026-10-09
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-107845"
kev: false
cvss: 9.3
epss: 0.00272
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-107845: Contao: Cross-site scripting in the comments bundle

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.3% , percentile 18: FIRST’s model estimates a 0.3% chance of exploitation activity in the next 30 days, higher than 18% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
- Only applies if your dependency tree includes contao/comments-bundle (Composer (PHP)) >= 4.0.0, < 5.3.50, fixed in 5.3.50 ; contao/comments-bundle (Composer (PHP)) >= 5.4.0-RC1, < 5.7.12, fixed in 5.7.12 . Check your lockfile, including transitive dependencies.

## What it is

Contao is an Open Source CMS. From version 4.0.0 until 5.3.50 and 5.7.12, an unauthenticated visitor can submit a comment whose email or website metadata is rendered without sufficient attribute and URL encoding by listComments() in comments-bundle/contao/dca/tlcomments.php. When a backend user opens the Comments module, attacker-controlled script can execute in the Contao backend origin under that user's session. Unpublished comments remain visible to moderators, so moderation does not prevent exposure. This issue is fixed in versions 5.3.50 and 5.7.12.

## Affected packages

- Composer (PHP) `contao/comments-bundle` >= 4.0.0, < 5.3.50 → fixed: 5.3.50
- Composer (PHP) `contao/comments-bundle` >= 5.4.0-RC1, < 5.7.12 → fixed: 5.7.12

## Affected products (CVE record)

- contao contao: >= 4.0.0, < 5.3.50, >= 5.4.0-RC1, < 5.7.12

## Severity

- GitHub_M CVSS 3.1: 9.3 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.3 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.27% probability of exploitation activity in the next 30 days; percentile 18.

## Sources

- [GitHub Advisory GHSA-628f-v4f6-p37r](https://github.com/advisories/GHSA-628f-v4f6-p37r)
- [CVE.org record CVE-2026-107845](https://www.cve.org/CVERecord?id=CVE-2026-107845)
- [NVD entry CVE-2026-107845](https://nvd.nist.gov/vuln/detail/CVE-2026-107845)
- [github.com](https://github.com/contao/contao/security/advisories/GHSA-628f-v4f6-p37r)
- [github.com](https://github.com/contao/contao/commit/22505d5f79bc1a7f52e2cba5fddf6007e1f0408a)
- [github.com](https://github.com/contao/contao/releases/tag/5.3.50)
- [github.com](https://github.com/contao/contao/releases/tag/5.7.12)

---
Source page: https://erroneo.us/security/cve/CVE-2026-107845/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt