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

[email protected] reports:

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.