tarteaucitron: data-cookie attribute can be used to delete arbitrary cookies

Summary

tarteaucitron provides a list of cookies and buttons to delete them. If an attacker can write HTML with data attributes, they could create an element that silently deletes a cookie when clicked and trick a user to delete this cookie.

Details

tarteaucitron.cookie.purge() is called on any element with the purgeBtn class. It does not check if the element is a legitimate tarteaucitron button or if the cookie corresponds to a service handled by tarteaucitron.

PoC

<a class="purgeBtn" data-cookie="foo">Click me!</a>

If someone has a cookie with this name and clicks on the link, the cookie is silently deleted.

Impact

The impact is limited because this only works on cookies without HttpOnly=true and the attacker has to know the name of the cookie.