Drupal core’s form API has a vulnerability where certain contributed or custom modules’ forms may be vulnerable to improper input validation. This could allow an attacker to inject disallowed values or overwrite data. Affected forms are uncommon, but in certain cases an attacker could alter critical or sensitive data.

We do not know of affected forms within core itself, but contributed and custom project forms could be affected. Installing this update will fix those forms.

This advisory is not covered by Drupal Steward.