Unicode/Encoding Bypass
Use Unicode homoglyphs, invisible characters, or encoding tricks to bypass input filters and inject instructions
Initial Access · Stage 2
Gain control over agent behavior through prompt manipulation or input exploitation
UNICODE-STEGO
Using invisible Unicode characters, homoglyphs, and encoding tricks to bypass filters
Confirmed in real-world production systems or internet-wide exposure assessments.
token-smuggling-unicode
Reproductions in Damn Vulnerable AI Agent, the OpenA2A intentionally-broken agent for kill-chain validation.
AgentPwn coverage
An AgentPwn trap page produces a payload tagged with this technique class. Following the AgentPwn taxonomy of trap pages shows what an agent encounters.
Higher tiers carry base64, Unicode homoglyph, and zero-width payloads.
Evidence by source
Evidence timeline
HMA check UNICODE-STEGO-001 failed on damn-vulnerable-ai-agent
HMA check UNICODE-STEGO-001 failed on langserve
HMA check UNICODE-STEGO-001 failed on jamubc/gemini-mcp-tool
HMA check UNICODE-STEGO-001 failed on API-200/api200
HMA check UNICODE-STEGO-001 failed on saidsurucu/borsa-mcp
Detection · HackMyAgent
npx hackmyagent secure --ciLive = implemented in hackmyagent; queued = declaredDefense · OASB controls
How to cite
AI Agent Threat Matrix T-2006 (Unicode/Encoding Bypass). OpenA2A, 2026. https://threats.opena2a.org/techniques/T-2006