Apple has released QuickTime 7.6, its flagship multimedia framework that capable of handling various media formats of digital video, media clips, sound, text, animation, music, and interactive panoramic images. QuickTime player is required to playback some media file in proprietary Apple format, particular QuickTime .mov file format, which is been used to stream high definition (HD) movie trailers.

QuickTime 7.6 includes changes that increase reliability, improve compatibility and enhance security, according to HT3292 and HT3403:

Video:

Improves single-pass H.264 encoding quality
Increases the playback reliability of Motion JPEG media

Audio:

Improves AAC encoding fidelity
Audio tracks from MPEG video files now export consistently

Application Support:

Improves compatibility with iChat and Photo Booth

Security:

Fixes accessing a maliciously crafted RTSP URL may lead to an unexpected application termination or arbitrary code execution.
Fixes viewing a maliciously crafted QTVR movie file may lead to an unexpected application termination or arbitrary code execution.
Fixes vewing a maliciously crafted AVI movie file may lead to an unexpected application termination or arbitrary code execution.
Fixes viewing a maliciously crafted movie file may lead to an unexpected application termination or arbitrary code execution during handling of MPEG-2 video files with MP3 audio content, H.263 encoded movie files, Cinepak encoded movie files and jpeg atoms in QuickTime movie files.

As usual, latest version of QuickTime can be downloaded from official QuickTime site, or user can download directly the setup installer of QuickTime 7.6 using direct download links below.

QuickTime 7.6 for Mac OS X Leopard: QuickTime76_Leopard.dmg
QuickTime 7.6 for Mac OS X Tiger: QuickTime76_Tiger.dmg
QuickTime 7.5 for Mac OS X Pather: QuickTime75_Panther.dmg
QuickTime 7.60.92.0 for Windows: QuickTimeInstaller.exe

Update: QuickTime 7.6.2