Literally one of the worst formats I deal with daily, from a security standpoint are PDFs. Very useful and predictable for the end user; yes, but very dangerous for the capabilities it allows.

Dangerzone works like this: You give it a document that you don't know if you can trust (for example, an email attachment). Inside of a sandbox, Dangerzone converts the document to a PDF (if it isn't already one), and then converts the PDF into raw pixel data: a huge list of RGB color values for each page. Then, in a separate sandbox, Dangerzone takes this pixel data and converts it back into a PDF.