from support:

Firstly ,glad to hear that you have solved the probem .And i will feed back this issue to my senior engineer.Sorry for the trouble bringing to you.
Secondly,the security means that you can secure your wireless network.For how to secure,please refer to:
http://www.tp-link.com/en/article/?faqid=399

The security meassures on that link I have already taken but got no feedback
on the impact of running old firmware.

I didn't mean ordinary security but weaknesses in firmware regarding
"1. Added session mechanism to improve security;" as stated in
release of new firmware. As I am running the old one without session mechanism
I wanted a statement on it's affect on my system.

the link is regarding safety of wireless network, my main concern is the
safety of wan-ip port. If that is more susceptible to attack?

Maybe it is vulnerable to something like
BASH bug "shellshocked"

I see here that they aint vulnerable to shelshock
http://forum.tp-link.com/showthread.php?77578-Notification-TP-LINK-products-are-not-affected-by-Shellshock
but something like it


any input on that?

Obviously, TP-LINK people misunderstood what security you are talking about.
As stated, TP-LINK engineers have checked its product portfolios and the result is that TP-LINK wireless router, ADSL router, wireless AP, SMB router and switch products are NOT affected by the “Shellshock” bash bug.