Its not just IOS. PDFs cause security problems everywhere where they are collected, and have been - for years.
We are running a service which collects documents from our consumers. We have a content disarm service which is basically a blast-proof container without any access rights, fed a stream of source bytes and outputting clean PDFs. Not a month passes without a burst of attempts at poisoning our systems with malicious PDFs. I don't remember when was the last time that we had attempts driven by malicious jpegs or pngs, just PDFs. Its one of those uber-shit Turing-complete file formats that should die long ago.
We are running a service which collects documents from our consumers. We have a content disarm service which is basically a blast-proof container without any access rights, fed a stream of source bytes and outputting clean PDFs. Not a month passes without a burst of attempts at poisoning our systems with malicious PDFs. I don't remember when was the last time that we had attempts driven by malicious jpegs or pngs, just PDFs. Its one of those uber-shit Turing-complete file formats that should die long ago.