The QTKit allows multiplexing between QuickTime X and QuickTime 7 behind the scenes so that the user need not worry about which version of QuickTime they need to use. Bugs and vulnerabilities QuickTime 7.4 was found to disable Adobe's video compositing program, After Effects. This was due to the DRM built into version 7.4 since it allowed movie rentals from iTunes. QuickTime 7.4.1 resolved this issue. Versions 4.0 through 7.3 contained a buffer overflow bug which could compromise the security of a PC using either the QuickTime Streaming Media client, or the QuickTime player itself. The bug was fixed in version 7.3.1. QuickTime 7.5.5 and earlier are known to have a list of significant vulnerabilities that allow a remote attacker to execute arbitrary code or cause a denial of service (out-of-bounds memory access and application crash) on a targeted system. The list includes six types of buffer overflow, data conversion, signed vs. unsigned integer mismatch, and uninitialized memory pointer. QuickTime 7.6 has been found to disable Mac users' ability to play certain games, such as Civilization IV and The Sims 2. There are fixes available from the publisher, Aspyr. QuickTime 7 lacks support for H.264 Sample Aspect Ratio. QuickTime X does not have this limitation, but many Apple products (such as Apple TV) still use the older QuickTime 7 engine. iTunes previously utilized QuickTime 7, but as of October 2019, iTunes no longer utilizes the older QuickTime 7 engine. QuickTime 7.7.x on Windows fails to encode H.264 on multi-core systems with more than approximately 20 threads, e.g. HP Z820 with 2× 8-core CPUs. A suggested solution is to disable hyper-threading/limit CPU cores. Encoding speed and stability depends on the scaling of the player window. On April 14, 2016, Christopher Budd of Trend Micro announced that Apple has ceased all security patching of QuickTime for Windows, and called attention to two Zero Day Initiative advisories, ZDI-16-241 and ZDI-16-242, issued by Trend Micro's subsidiary TippingPoint on that same day. Also on that same day, the United States Computer Emergency Readiness Team issued alert TA16-105A, encapsulating Budd's announcement and the Zero Day Initiative advisories. Apple responded with a statement that QuickTime 7 for Windows is no longer supported by Apple. See also AVFoundation Comparison of audio player software Comparison of video player software Perian Qtch QuickTime Alternative QuickTime Broadcaster QuickTime File Format QuickTime Streaming Server Darwin Streaming Server Windows Media Components for QuickTime