TP-Link C2 and C20i devices through firmware 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n have too permissive iptables rules, e.g., SNMP is not blocked on any interface.

vsftpd on TP-Link C2 and C20i devices through firmware 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n has a backdoor admin account with the 1234 password, a backdoor guest account with the guest password, and a backdoor test account with the test password.

TP-Link C2 and C20i devices through firmware 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n allow DoSing the HTTP server via a crafted Cookie header to the /cgi/ansi URI.

TP-Link C2 and C20i devices through firmware 0.9.1 4.2 v0032.0 Build 160706 Rel.37961n allow remote code execution with a single HTTP request by placing shell commands in a "host=" line within HTTP POST data.