An attacker can build a link to your Drupal site that shows content of their choosing, and send it to people. Anyone who opens it sees a defaced page. Drupal's advisory says the change isn't stored, and only appears when someone opens that specific link. The page shows only the attacker's content, without your site's branding or other content.

Who is affected

Every site on an affected version of drupal/core. Drupal says all module configurations are exploitable and no login is needed. The attack only works on someone who opens the crafted link, so the main risk is phishing or embarrassment rather than data loss.

What to do

Update to the fixed release for your branch:

  • Drupal 10.4: update to 10.4.9
  • Drupal 10.5: update to 10.5.6
  • Drupal 11.1: update to 11.1.9
  • Drupal 11.2: update to 11.2.8

Drupal 11.0.x, 10.3.x and older no longer get security fixes, so move to a supported branch.

Reported by Kevin Quillen.