updates - Is having Lubuntu 12.04 a security risk?

I have a computer with Lubuntu 12.04 installed. Since unlike Ubuntu 12.04 Lubuntu is not LTS, I will not get Lubuntu updates.

However, I am still getting updates (I guess these are the general Ubuntu Updates).
Is having Lubuntu installed a security risk, or are the missing updates not security relevant?

Is it more secure to have Ubuntu installed and manually install the LXDE desktop? (The computer is a little bit to old for fluent use of the Unity desktop).

Thanks a lot!

Edit

I switched to 13.10 - still I am wondering what the answer to this question is.