I would agree with madbilly after all while reinvent the wheel when the present wheel presumably comes from a good stable.
This article (second last paragraph) highlights its evolution from Firefox OS to B2G to KaiOS.
I got confirmation from someone at KaiOS, it's gecko 48.
As for the evolution from FirefoxOS, it's not clear that anything from the community B2GOS project is actually used in KaiOS, maybe they just say that KaiOS is based on B2GOS to make it clear it's not developed from a public release of FirefoxOS but actually from some of the unreleased work (although still public, on GitHub, which is how KaiOS could fork it).
I do ebanking transaction via my desktop computer. Recently I tried to do it via the browser but got a message stating it needs to be upgraded to be compatible with CIMB Clicks webpage. I relayed this to KaiOS Technologies who replied they have forward my suggestion "to the product team, so they could consider updating the browser to the version 52 of Mozilla Firefox 52 or higher to make it compatible with CIMB Clicks."
That's very interesting. It's very very unlikely that the browser will be updated to v52, because in KaiOS the whole UI uses the same software as the browser - the Gonk and Gecko parts of FirefoxOS. Mozilla removed from Gecko (the browser engine) all parts needed for FirefoxOS after v48, this means that to update to v52 will mean that KaiOS have to update all the missing parts and build them back into Gecko. I know they have some talented people at KaiOS, but this is a big big job. Personally, I would be very happy to see them do it, but I still think it's unlikely.
More likely, but not definite, it that KaiOS will update the browser engine they use (v48) to be compatible with CIMB Clicks.
I wish for the first solution, but hope that you get at least the second :)
OIC, Well let's see what they come up so long as I can logon to CIMB Clicks is OK
I warn KaiOS Technologies that based on forums I've visited and participated, I would not be surprised that after the dateline set by themselves (end of 2018), if serious updates are not provided including WhatsApp, I would expect many Nokia 8110 4G customers will replace it with alternative that can. They replied and said tq for my insight.