Information Disclosure due to Out-of-scope Site Resolution

> ### CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:F/RL:O/RC:C (3.5)

Problem

In multi-site scenarios, enumerating the HTTP query parameters id and L allowed out-of-scope access to rendered content in the website frontend. For instance, this allowed visitors to access content of an internal site by adding handcrafted query parameters to the URL of a site that was publicly available.

Solution

Update to TYPO3 versions 9.5.42 ELTS, 10.4.39 ELTS, 11.5.30, 12.4.4 that fix the problem described above.

> ℹ️ Strong security defaults - Manual actions required
> Resolving sites by the id and L HTTP query parameters is now denied per default. However, it is still allowed to resolve a particular page by e.g. https://example.org/?id=123&L=0 - as long as the page-id 123 is in the scope of the site configured for the base-url example.org.
> The new feature flag security.frontend.allowInsecureSiteResolutionByQueryParameters - which is disabled per default - can be used to reactivate the previous behavior.

Credits

Thanks to Garvin Hicking who reported this issue, and to TYPO3 core & security team members Oliver Hader and Benjamin Franzke who fixed the issue.

References

• TYPO3-CORE-SA-2023-003