PrestaShop cross-site scripting via customer contact form in FO, through file upload

Impact

Only PrestaShops with customer-thread feature flag enabled are impacted, starting from PrestaShop 8.1.0.

The impact is substantial, when the customer thread feature flag is enabled, through the front-office contact form, a hacker can upload a malicious file containing an XSS that will be executed when an admin opens the attached file in back office.

Consequence: the script injected can access the session and the security token, which allows it to perform any authenticated action in the scope of the administrator’s right.

Patches

This vulnerability is patched in 8.1.6.

Workarounds

As long as you have not upgraded to 8.1.6, a simple workaround is to disable the customer-thread feature-flag.

Thank you to Ayoub AIT ELMOKHTAR, who discovered this vulnerability and share it with the PrestaShop team.