Impact

It is possible to inject insert tags in front end forms which will be replaced when the page is rendered.

Patches

Update to Contao 4.4.52, 4.9.6 or 4.10.1.

Workarounds

Disable the front end login form and do not use form fields with array keys such as fieldname[].

References

https://contao.org/en/security-advisories/insert-tag-injection-in-forms

For more information

If you have any questions or comments about this advisory, open an issue in contao/contao.