Impact
Authenticated users can inject malicious code in widgets with units, which is then executed both in the element preview (back end) and on the website (front end).
Patches
Update to Contao 4.9.42, 4.13.28 or 5.1.10.
Workarounds
Disable login for all untrusted back end users.
References
https://contao.org/en/security-advisories/cross-site-scripting-in-widgets-with-units
For more information
If you have any questions or comments about this advisory, open an issue in contao/contao.
Credits
Thanks to Christian Pöschl and Fabian Brenner from usd AG for reporting this vulnerability.
Contao is an open source content management system. Prior to versions 4.9.40, 4.13.21, and 5.1.4, logged in users can list arbitrary system files in the file manager by manipulating the Ajax request. However, it is not possible to read the contents of these files. Users should update to Contao 4.9.40, 4.13.21 or 5.1.4 to receive a patch. There are no known workarounds.
Impact
It is possible to inject code into the tllog table that will be executed in the browser when the system log is called in the back end.
Patches
Update to Contao 4.9.16 or 4.11.5.
Workarounds
Disable the system log module in the back end for all users (especially admin users).
References
https://contao.org/en/security-advisories/cross-site-scripting-in-the-system-log-2021
For more information
If you have any questions or comments about this advisory, open an issue in contao/contao.
Impact
It is possible for untrusted users to inject malicious code into HTML attributes in the back end, which will be executed both in the element preview (back end) and on the website (front end).
Installations are only affected if there are untrusted back end users who have the rights to modify HTML fields (e.g. TinyMCE).
Patches
Update to Contao 4.4.56, 4.9.18 or 4.11.7
Workarounds
Disable all fields that allow HTML for untrusted back end users or disable the login for these users.
References
https://contao.org/en/security-advisories/cross-site-scripting-via-html-attributes-in-the-back-end
For more information
If you have any questions or comments about this advisory, open an issue in contao/contao.
Credits
Thanks to Mikhail Khramenkov and Moritz Vondano for reporting this security issue.
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.