Kirby is a CMS targeting designers and editors. Kirby allows to restrict the permissions of specific user roles. Users of that role can only perform permitted actions. Permissions for creating and deleting languages have already existed and could be configured, but were not enforced by Kirby's frontend or backend code. A permission for updating existing languages has not existed before the patched versions. So disabling the languages.* wildcard permission for a role could not have prohibited updates to existing language definitions. The missing permission checks allowed attackers with Panel access to manipulate the language definitions. The problem has been patched in Kirby 3.6.6.6, Kirby 3.7.5.5, Kirby 3.8.4.4, Kirby 3.9.8.2, Kirby 3.10.1.1, and Kirby 4.3.1. Please update to one of these or a later version to fix the vulnerability. There are no known workarounds for this vulnerability.

Affected: Packagist: getkirby/cms

### TL;DR

This vulnerability affects all Kirby sites with enabled `languages` option that might have potential attackers in the group of authenticated Panel users.

If you have disabled the `languages` and/or `api` option and don't call any methods in your code that cause a write access to languages (language creation, update or deletion), your site is *not* affected.

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### Introduction

Kirby allows to restrict the permissions of specific user roles. Users of that role can only perform permitted actions.

Permissions for creating and deleting languages have already existed and could be configured, but were not enforced by Kirby's frontend or backend code.

A permission for updating existing languages has not existed before the patched versions. So disabling the `languages.*` wildcard permission for a role could not have prohibited updates to existing language definitions.

### Impact

The missing permission checks allowed attackers with Panel access to manipulate the language definitions.

The language definitions are at the core of multi-language content in Kirby. Unauthorized modifications with malicious intent can cause significant damage, for example:

- If the `languages` option was enabled but no language exists, creating the first language will switch Kirby to multi-language mode. - Deleting an existing language will lead to content loss of all translated content in that language. Deleting the last language will switch Kirby to single-language mode. - Updating…