October CMS stored XSS by authenticated backend user with improper configuration

Impact

A user with access to the media manager that stores SVG files could create a stored XSS attack against themselves and any other user with access to the media manager when SVG files are supported.

SVG files are supported by default in v3 for convenience; however, this has resulted in multiple mistaken vulnerability reports from security researchers. As per the documentation, if a backend user is not trusted, the advice is to remove the svg extension from the list of supported file types.

Patches

The issue has been patched in v3.5.2 by including an SVG sanister. It is enabled by default for new installations but must be enabled for existing sites in the config/media.php file.

'clean_vectors' => true,

Workarounds

If you cannot upgrade for this patch, follow the pervious advice and remove svg from the supported file types.

References

• https://github.com/octobercms/october/blob/3.x/config/media.php

Credits to:

• Faris Krivic
• Okan Kurtulus
• Aldin Visnjic
• Bug Shankar

For more information

If you have any questions or comments about this advisory:

• Email us at [email protected]