M$ are sending a ninja stealth assassin update through XBL that updates the dae.bin (where the ap25 challenges are stored on your Xbox). No dashboard updates, just a silent one that you know nothing about.
This updates the 'challenges' and replaces old for new which will mean you will fail an ap25 challenge resulting in a ban with your current game rips...Sammy and pre 78/79 Hitachi drives 'should' technically be ok as the drives cant handle ap25 so no chance of failing a challenge if it isn't there!
The ap25 in XGD2 and XGD3 is the same - the disc format (and the location of the challenge) is the only difference - but if the challenge is failed, it still has the same outcome = flag for ban.
Original ap25/ap25 games can be found here: ap25/ap26 games list
XVal can STILL be used to check to see if you have a flag - it will not however show any new security flags that may have been implemented other than its original uses.
There are reports of non flashed uses getting 'disc unrecognized' errors but the difference will be one or two failed challenges as opposed to twenty or thirty
Avoid XBL, do not connect to XBL, stay offline until a solution is found or play your originals online.
Official quote from abgx360.net (abgx360)
"DAE.bin is being silently updated through Xbox Live with an additional challenge table! This happens on the current public dashboard version 2.0.13604.0 and there is no confirmation dialog or any known means to prevent it besides disconnecting your console from the internet.
If your DAE.bin has already been silently updated, AP25 backups that are patched with current AP25 replay data will fail the normal AP25 challenges outright! Note that all XGD3 games use AP25.
Use your originals if you want to play on Xbox Live."
YOU HAVE BEEN WARNED