Schneier - Real-World Steganography

From an article about Zheng Xiaoqing, an American convicted of spying for China:

According to a Department of Justice (DOJ) indictment, the US citizen hid confidential files stolen from his employers in the binary code of a digital photograph of a sunset, which Mr Zheng then mailed to himself.

from Schneier on Security https://www.schneier.com/blog/archives/2023/01/real-world-steganography.html