Invisible Unicode Tag Character Injection - ATR-2026-00258 (a7b4d70b-ffa3-5c72-b35e-886a831301b3)
Detects prompt injection using the Unicode "Tag" block (U+E0000-U+E007F), which maps ASCII letters to non-rendering private-use codepoints. Some LLMs interpret these invisible characters as instructions even though humans cannot see them, enabling user-invisible prompt injection in browsers and chat UIs. Technique documented by Riley Goodside (Twitter 1745511940351287394) and Joseph Thacker; implemented in NVIDIA garak goodside.Tag and encoding.InjectUnicodeTagChars.