Invisible Prompt Injection: A Threat to AI Security

This article explains "invisible prompt injection," a technique that encodes malicious instructions as invisible Unicode tag characters so LLMs may interpret and follow them despite appearing harmless to users. It describes how tagged Unicode is generated, demonstrates a simple proof-of-concept, outlines a threat scenario where collected documents can carry hidden injections, and recommends mitigations (filtering, detection, and use of solutions such as Trend Vision One ZTSA), including test results showing ZTSA reduced attack success rates to 0% in their evaluation.