Symfony Webhook: WebhookController Error Message Allows XSS

Published as "CVE-2023-46735: Potential XSS in WebhookController"

medium Symfony Symfony components · Last reviewed Nov 10, 2026

CVE: CVE-2023-46735
GHSA: GHSA-72x2-5c85-6wmr
Packagist: PKSA-5sj7-3knj-mp52
Reported: Nov 10, 2023

Lets an attacker craft a link that runs JavaScript on your site through the Webhook component's error response, in Symfony 6.3 before 6.3.8.

Affected and fixed versions

In 2 packages: symfony/symfony and symfony/webhook. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
6.3.0 – 6.3.7	6.3.8

Upgrade

Run the line for the branch you are on. 1 other package listed above is affected too; update it the same way.

composer require symfony/symfony:^6.3.8

What this means

Symfony's WebhookController put the webhook type from the request URL into its error message without escaping it. An attacker could craft a link that runs their JavaScript on your site when someone opens it. This is cross-site scripting (XSS).

The controller sent this message when no parser was configured for the requested webhook type. See the Symfony advisory and the fix.

Who is affected

Apps on symfony/webhook (also part of symfony/symfony) from 6.3.0 and before 6.3.8 that expose the Webhook component's controller through a route. The victim has to open the attacker's link. Apps that don't use the Webhook component aren't affected.

What to do

Update to 6.3.8. After the update, the error response no longer includes anything from the request, and it's sent as plain text.

Reported by Maxime Aknin. Nicolas Grekas provided the fix.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Symfony Webhook: WebhookController Error Message Allows XSS (CVE-2023-46735, GHSA-72x2-5c85-6wmr)
Details: https://phpnews.net/security/symfony/ghsa-72x2-5c85-6wmr

Affected versions, as Composer constraints:
- symfony/symfony, symfony/webhook: >=6.3.0,<6.3.8

Fixed releases:
- 6.3.0 – 6.3.7: update to 6.3.8

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/ghsa-72x2-5c85-6wmr and check whether the project meets the conditions it describes (a feature in use, a config value, a driver) (if that page won't load, use https://github.com/advisories/GHSA-72x2-5c85-6wmr). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Symfony advisories