Is there a copy of the gif available? That’s interesting
I wouldn't even know how to look for something unusual in a gif's source code but I also feel this is the most compelling part. I wish they'd uploaded it.
GIF stands out as a widely understood file format [1][2].
To kick things off, delve into the GIF file using a hexadecimal editor. HexFiend [3], for instance, offers a template for visualizing GIF file structures [4]. Another excellent option is Synalyze It! [5], which comes pre-loaded with an extensive list of file formats, encompassing GIF among others.
These visualizations serve as a guide to pinpoint any irregular byte clusters that might pose issues when loading the file into an application with an image reader lacking support for that specific byte group or its arrangement. Once you've identified such a cluster, consider it the bug.
[1] https://en.wikipedia.org/wiki/GIF#Example_GIF_file
[2] https://www.w3.org/Graphics/GIF/spec-gif89a.txt
[4] https://github.com/HexFiend/HexFiend/blob/master/templates/I...