The CakeResponse::download() method in lib/Cake/Network/CakeResponse.php constructs a Content-Disposition header by directly interpolating a caller-supplied filename into a quoted-string value without sanitization. Two distinct injection vectors exist in the unpatched code. First, if the filename contains C0 control characters (CR or LF), PHP refuses to emit the entire Content-Disposition header, silently dropping the attachment disposition. The response body is then served with its own Content-Type (for example text/html for an .html attachment) and renders inline in the browser on the application origin, creating a stored cross-site scripting condition. The commit message notes this is reachable even when the download_attachments_on_load setting is enabled, meaning a victim merely needs to view a page that triggers the download. Second, a double-quote character in the filename terminates the quoted-string value early, permitting injection of additional Content-Disposition parameters. The affected code path covers all callers of CakeResponse::download(), including attribute downloads, proposal downloads, and restSearch exports. An authenticated user who can create or upload an attachment with a crafted filename (for example through MISP attribute naming or proposal attachment naming) can store the malicious filename. When any other authenticated user views the affected page, the unsanitized filename is reflected into the HTTP response header, resulting in header manipulation and potential execution of arbitrary HTML or JavaScript in the context of the application origin. The security impact is equivalent to a stored cross-site scripting vulnerability, allowing session hijacking, data exfiltration, and unauthorized actions on behalf of the victim.