The issues addressed pertain only to computers running Windows 7, Vista or XP with service pack 2 or later, with 14 of the 17 flaws credited to research involving HP's Zero Day Initiative.
Many of the fixes in Quicktime 7.7.2 had to do with heap, buffer, stack and integer overflows when viewing maliciously coded files, while others dealt with memory corruption and file handling issues. All of the bugs caused unexpected program termination, arbitrary code execution, or both, though none were reported to have been exploited.
The Zero Day Initiative, founded by TippingPoint which is now part of HP, pays a bounty for independent researchers to find bugs which are subsequently passed along to software makers for resolution.
More information about the specific flaws can be found through Apple's Quicktime 7.7.2 support page while the Windows-only update can be downloaded here.