This is why Firefox chose to implement a custom PDF reader in pure JS for better sandboxing leveraging the existing browser JS sandboxing. As a side effect, it'

This is why Firefox chose to implement a custom PDF reader in pure JS for better sandboxing leveraging the existing browser JS sandboxing. As a side effect, it's been a helpful JS library for embedding PDFs on websites. The Chrome PDF parser, originating from Foxit (now open-sourced as PDFium), has been the source of many exploits in Chrome itself over the years.