Impact

Users can upload SVG files with malicious code, which is then executed in the back end and/or front end.

Patches

Update to Contao 4.13.54, 5.3.30 or 5.5.6.

Workarounds

Remove svg,svgz from the allowed upload file types in the system settings and from contao.editablefiles in the config.yaml.

References

https://contao.org/en/security-advisories/cross-site-scripting-through-svg-uploads

For more information

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