The Portable Document Format (PDF) specification does not provide any information regarding the concrete procedure of how to validate signatures

The Portable Document Format (PDF) specification does not provide any information regarding the concrete procedure of how to validate signatures. Consequently, a Signature Wrapping vulnerability exists in multiple products. An attacker can use /ByteRange and xref manipulations that are not detected by the signature-validation logic. This affects Foxit Reader before 9.4 and PhantomPDF before 8.3.9 and 9.x before 9.4. It also affects eXpert PDF 12 Ultimate, Expert PDF Reader, Nitro Pro, Nitro Reader, PDF Architect 6, PDF Editor 6 Pro, PDF Experte 9 Ultimate, PDFelement6 Pro, PDF Studio Viewer 2018, PDF Studio Pro, PDF-XChange Editor and Viewer, Perfect PDF 10 Premium, Perfect PDF Reader, Soda PDF, and Soda PDF Desktop.