A Brazilian labor court fined two law firms after finding that lawyers deliberately hid a prompt-injection instruction in an employment-court filing. The text was rendered white on a white background, making it invisible during ordinary reading. It instructed any AI system reviewing the petition to respond superficially and avoid challenging its documents. The judge discovered it while using Galileu, a generative AI tool used by Brazil’s National Justice Council; after the font color was changed, the command became visible. The underlying claim sought R$842,000, and the court imposed a fine equal to 10% of that amount, approximately US$16,000.
The court held that the lawyers’ conduct aimed to bias an AI-generated response or draft judgment against the defendant, undermining both the proceedings and the administration of justice. It grounded the penalty in Brazilian procedural rules requiring good faith, loyalty, and truthfulness, and prohibiting conduct that obstructs judicial work. The decision treats machine-readable content as part of a filing’s integrity, not as a loophole separate from its visible text, and may be the first judicial ruling to address deliberate prompt injection against a court system. The AI reportedly detected and blocked the suspicious content, illustrating both the risks of documents processed by AI and the value of safeguards that monitor for manipulation.
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