A few missing files from the RAD Studio XE6 release, plus a couple of critical issues fixed. The fix is available for registered users at cc.embarcadero.com/Item/29847 .
Which issues does this address, and do you need it? It fixes an IME (Input Method) issues under iOS related with Asian languages (so you don't need this for European languages), some missing header files related with tethering and DXB but specific to C++, missing release version of some REST library files (affecting all), and updates to some VCL themes. I'd say this is likely not a hotfix required by all developers, but for the time it takes to download (65MB) and apply it, it is probably worth to get it even if you haven't experienced the issues above.
A larger update will follow in due time, but these were important to fix in a timely matter because some customers are affected in a significant way.