Canon has warned that Wi-Fi connection settings stored in the memory of some of its inkjet printers may not be deleted by the usual initialization process and pose a security risk when disposed of.
The number of printers this vulnerability affects is massive and encompasses 196 total models. It includes the home and business E, G, GM, GX, iB, iP, MB, MG, MX, TR, TS, and XK inkjet series as well as the Pro series photo printers (which includes everything from the Pro-10 through the Pro-1000 printers). It also affects some large format printers including Canon’s Pro line (Pro-520 through Pro-6100S) as well as the TM, TX, GP, and TC series printers. The full list of all affected printers can be found on Canon’s website.
When one of these printers comes into the hands of a third party (such as in the case of repair, loaning it out, or when throwing it away), Wi-Fi connection information is still stored on the device even if it has been initialized through the normal process.
Bleeping Computer notes that those who are aware of the vulnerability could pull the information off the printers which would give them access to the a home Wi-Fi network. The exact information that is stored on the device varies per printer, but it will usually include network SSID, the password, network type, assigned IP address, MAC address, and network profile. read more here