While the title refers to "arbitrary data," users can hide whatever they want within Unicode characters, though this seems limited to text. This is different from, say, "arbitrary code execution ...

but they also have a pre-built Unicode point. There are also ligatures that combine multiple characters into a single code point. Suddenly it isn’t so clear what character equality even means ...

As long as you’ve memorized the code for your favorite special character, you can insert it in less than a second with the proper key presses. Shortcut Character Unicode Description Emoticons ...