CVE-2026-75529 describes a stored cross-site scripting vulnerability in the Pandora-analysis pandora product affecting versions up to 1.12.5. The issue occurs in the /task-download/<task_id>/.../pdf endpoint, which verifies submitted files as PDFs using content-based detection but returns them using Flask's send_file without explicitly specifying MIME type or forcing download as an attachment. Because Flask infers MIME type from the filename, an attacker can craft a polyglot PDF file whose filename causes the response to be served with an executable MIME type (e.g., HTML). This enables execution of attacker-controlled scripts in the victim's browser within the Pandora application's security context. The patch fixes this by explicitly setting Content-Type to application/pdf, forcing Content-Disposition to attachment, and using a trusted filename based on the task UUID.

Successful exploitation allows an attacker to execute arbitrary scripts in the security context of the Pandora application for users who access the malicious PDF download link. This could lead to unauthorized access to application data or actions using the victim's session. The vulnerability is rated medium severity with a CVSS 4.0 base score of 6.9, indicating a significant but not critical risk.

A patch is available that explicitly sets the Content-Type header to application/pdf, forces the Content-Disposition header to attachment, and assigns a trusted .pdf filename based on the task UUID. Users should upgrade to a fixed version beyond 1.12.5 to remediate this vulnerability. No additional mitigations are indicated by the vendor advisory.