Clipboard based cross-site scripting (blocked with default CSP) in Kanboard

Kanboard is project management software that focuses on the Kanban methodology. Due to improper handling of elements under the contentEditable element, maliciously crafted clipboard content can inject arbitrary HTML tags into the DOM. A low-privileged attacker with permission to attach a document on a vulnerable Kanboard instance can trick the victim into pasting malicious screenshot data and achieve cross-site scripting if CSP is improperly configured. This issue has been patched in version 1.2.29.