CVE-2020-8167: CSRF

There is a vulnerability in rails-ujs that allows attackers to send CSRF tokens to wrong domains.

Versions Affected: rails <= 6.0.3 Not affected: Applications which don't use rails-ujs. Fixed Versions: rails >= 5.2.4.3, rails >= 6.0.3.1

Impact ------

This is a regression of CVE-2015-1840.

In the scenario where an attacker might be able to control the href attribute of an anchor tag or the action attribute of a form tag that will trigger a POST action, the attacker can set the href or action to a cross-origin URL, and the CSRF token will be sent.

Workarounds -----------

To work around this problem, change code that allows users to control the href attribute of an anchor tag or the action attribute of a form tag to filter the user parameters.

For example, code like this:

linkto params

to code like this:

linkto filteredparams

def filteredparams # Filter just the parameters that you trust end