OpenProject: Stored XSS on openproject.example.com through /api/v3/projects/{project}/work_packages via POST parameter "description"

OpenProject is open-source, web-based project management software. Prior to 17.3.3 and 17.4.1, the HTML sanitizer grants elements unrestricted data-* attributes via :data wildcard. An attacker injects data-controller="poll-for-changes" into a work package description, causing Stimulus.js to mount a controller that fetches an attacker-uploaded attachment and passes it to renderStreamMessage(). This executes arbitrary Turbo Stream actions — including redirect_to — in every victim's authenticated browser session, redirecting them to an attacker-controlled server. This vulnerability is fixed in 17.3.3 and 17.4.1.