When I load the attached JPEG in Safari 9.0.3 (or WebKit nightly) on my iMac, the last few columns of pixels decode incorrectly. This only occurs on my iMac (Retina 5K, 27-inch, Late 2014) running 10.11.3. It does not occur on any other device that I own (I tested multiple iOS devices, my MacBook Pro, and my housemate's iMacs). Attached is a movie of me reloading the JPEG in question. Notice that the last column changes randomly. Other JPEGs do not exhibit this behavior, it may only occur when the width is 666 pixels and the color space is Grayscale. I vaguely recall running all of my images through an optimizer, so it's possible that the JPEG itself is invalid (I still wanted to file, however, in case this is exposing a memory issue in the decoder).
Created attachment 271118 [details] Image which decodes improperly on my iMac.
Created attachment 271120 [details] Video of me reloading the image in question. Notice the far-right column of pixels.
Note: Image is fine in Chrome, Firefox, Quicklook, Finder, Preview, Photoshop, and Mail.
<rdar://problem/24644825>
Thank you for the report! Since it's hardware specific, I think that this is an issue below WebKit (even though it doesn't reproduce in Preview). The problem will be tracked internally by Apple.