OHIF Viewers is a zero-footprint DICOM viewer with shared extension packages. From 3.5.0-beta.0 until 3.12.15, 3.13.7, and 3.14.0-beta.19, the dicom-pdf extension reads the attacker-controlled MIMETypeOfEncapsulatedDocument value in extensions/dicom-pdf/src/getSopClassHandlerModule.js and uses it as the Blob media type for the attacker-controlled EncapsulatedDocument bytes. When a victim opens Encapsulated PDF SOP Class 1.2.840.10008.5.1.4.1.1.104.1, extensions/dicom-pdf/src/viewports/OHIFCornerstonePdfViewport.tsx embeds the Blob URL in an object element. A Blob labeled as HTML is handled as HTML despite the application/pdf object hint, and the Blob inherits the OHIF origin, allowing embedded script to access session storage, authentication tokens, and same-origin PACS requests. The malicious DICOM object may be opened locally, uploaded to a shared PACS, or supplied by a DICOMweb source. This issue is fixed in source versions 3.12.15, 3.13.7, and 3.14.0-beta.19.