By chaining the selectors together, he was able to encode invisible messages inside an emoji (or any other Unicode character) ...

The concept revolves around Unicode's system of representing text as a sequence of codepoints, with each codepoint being a number assigned meaning by the Unicode Consortium.

Butler said it is highly unlikely that anyone would be able to use this method to hide malware or malicious code in an emoji.

Paul Butler tests and demonstrates the flexibility of encoding hidden messages within Unicode characters, including emoji.

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 ...

With multi-byte, variable-width character strings, the usual functions like strlen fall apart. Unicode’s combining characters also causes problems when it comes to comparison and collation of text.