/usr/lib/lua/luci/websys.lua on TP-LINK IPC TL-IPC223(P)-6, TL-IPC323K-D, TL-IPC325(KP)-*, and TL-IPC40A-4 devices has a hardcoded zMiVw8Kw0oxKXL0 password.
https://www.us-cert.gov/ncas/bulletins/SB18-155
https://github.com/yough3rt/IOT-pwn-for-fun/blob/master/TP-LINK-login-Escalation-of-Privileges