We have seen claims that the luxury hotel chain has suffered a credit card breach (some outlets are now confirming it). 

The last confirmation I received was that the chain is working with its banking partners to investigate the claims. We don't know yet if the breach impact some or all of its global properties. Unnamed sources say the breach goes back to just before christmas 2014. 

It is too soon to speculate how they were stolen. Some outlets jumped the gun and claimed the chains main reservation system was breached but it is important to remember that the breach could be on a Point of Sale terminal in the hotel (store, restaurant, etc).

Since the chain is made up of luxury properties, its patrons typically have high value credit cards that could fetch a premium in the credit card sale black market. 

If I am made aware of any developments, I will update this post accordingly.

For the record, I have stayed on many of their asian properties and I love the Mandarin Oriental chain.