Quite some time ago, I played around with some Computrend 902 Powerline adapters and found a number of different security issues - here and here.
Those devices are long gone, but whilst the issues I found were relatively minor (if nothing else, proximity was required) it left me a little concerned about the security of any devices that might replace them. For quite some time, I didn't need to use any powerline adapters, but eventually the need arose again (no practical way to run CAT-5 to the location and the Wifi reception is too spotty).
So I bought 2 pairs of On-Networks' PL500S Powerline adapters. Depending where you buy them from, the model number may be PL500P, PL500-UKS, or even the Netgear part number - Netgear ON NETWORKS PL500-199UKS.
I've not got as far as giving them a serious hammering from a security perspective as yet, however there doesn't seem to be much information about these devices available on the net (and what is there is potentially misleading), so I thought I'd post the information I've pulled together from prodding the devices, as well as a few common sense facts that might be being missed. As I'd have found some of the information helpful had it been available prior to purchase, I suspect others might find it of use too.