The WOPI API integration for Vereign Collabora CODE through 4.2.2 does not properly restrict delivery of JavaScript to a victim's browser, and lacks proper MIME type access control, which could lead to XSS that steals account credentials via cookies or local storage. The attacker must first obtain an API access token, which can be accomplished if the attacker is able to upload a .docx or .odt file. The associated API endpoints for exploitation are /wopi/files and /wopi/getAccessToken.