CVE-2026-75529 describes a stored cross-site scripting vulnerability in the Pandora analysis platform's PDF download endpoint (/task-download/<task_id>/.../pdf). The endpoint verifies submitted files as PDFs using content-based detection but returns files using Flask's send_file without explicitly specifying MIME type or forcing download as an attachment. Because Flask infers MIME type from filename, an attacker can submit a polyglot PDF file with a filename that causes the file to be served with an active MIME type (e.g., HTML). This allows execution of attacker-controlled scripts in the context of the Pandora application if a victim accesses the malicious file. The vulnerability is fixed by explicitly setting Content-Type to application/pdf, forcing Content-Disposition to attachment, and using a trusted .pdf filename derived from the task UUID.

Successful exploitation allows an attacker to execute arbitrary scripts in the victim's browser within the security context of the Pandora application. This could lead to unauthorized access to application data or actions using the victim's session. The vulnerability affects confidentiality and integrity of user sessions and data within Pandora. No privilege or user interaction is required beyond accessing the malicious PDF download link.

A patch is available that fixes the vulnerability by explicitly returning PDF downloads with Content-Type: application/pdf, forcing Content-Disposition: attachment, and assigning a trusted .pdf filename based on the task UUID. Users should upgrade to a version later than 1.12.5 where this fix is applied. Since no official fix version is explicitly stated, verify with the vendor advisory for the exact patched version. Until patched, avoid accessing PDF download links from untrusted sources.