A group of researchers from Israel's Ben-Gurion University of the Negev have shown how aftermarket parts for smartphones such as replacement
screens could be used to attack the device, or impersonate the user and exfiltrate data. The group has demonstrated that because most phones do not have a security check on it's display hardware, a replacement screen fitted with a microcontroller can be used to compromise a smartphone.
Pretty scary stuff when you think of how many screen replacements are done each year :\