A new attack, obviously. Unlimited is derived from Core v12 code versions, so an attacker familiar with the fixes done in the Core code in recent versions just have to use those vulnerabilities, one at a time, until the Unlimited developers keep in track with Core v14 fixes and their game will be over: no attacker will attack Unlimited without damaging Core too.
Do you have brain damage? The exploit, being the 5th so far, has
nothing to do with Core code. The exploit is related to Xthin, which is an inferior and crappy version of Compact blocks. Xthin does not exist in Bitcoin Core:
https://www.reddit.com/r/btc/comments/6a49mz/bu_under_attack_temporarily_disable_xthin_as/Who attacks Unlimited? Someone interested on the success of a different implementation.
A lot of individuals/groups attack Bitcoin Core each day. You have no point.
Who is interested in that success of Core v14/Segwit? Blockstream and those shills with an economic stake on Lightning implementation. It is so obvious who is doing this, and yet some people think they'll convince the rest it is because of Unlimited developers...
All the things that you've mentioned have nothing to do with each other.
Some people (Blockstream among others) would burn to ashes the Bitcoin network if they'll could just be the kings of those ashes For that reason, Unlimited supporters are not going to change our minds and we will keep running our nodes. Just disabling XThin as developers are recommending, until they release a patch. In two weeks we will have another attack and we will repeat the protocol. Not a big deal :-)
Anyone who supports Bitcoin Unlimited at this point is a shill or an outright idiot. Pick the one which better describes yourself.