A Brazilian Labor Court has fined two lawyers after finding a hidden Prompt injection in a filing submitted on behalf of a plaintiff. The instruction was written in white text on a white background, making it invisible to people reading the document but detectable when the formatting was changed.
According to the court’s ruling, the hidden message told the artificial intelligence system to respond to the petition superficially and not challenge its documents, regardless of any other instruction. The court described the method as prompt injection: the deliberate insertion of concealed instructions intended to manipulate an AI system processing a document.
The attempt ultimately had no effect on the outcome. The defendant did not respond to the allegations, so the plaintiff won by default. Nevertheless, the court characterized the lawyers’ conduct as offensive to the dignity of justice.
The ruling attributed responsibility to the two attorneys who signed the complaint. It said the plaintiff was not sufficiently familiar with the legal technicalities involved and had not had access to the document, making it unlikely that the plaintiff had inserted the hidden text. The lawyers were fined 10% of the award, an amount of approximately $16,000, and were reported to the state bar association and the Internal Affairs Department of the Regional Labor Court.
The case is not the first reported attempt to influence a court’s AI through concealed instructions. In another proceeding, a plaintiff placed a longer hidden prompt in a filing, which was discovered after a court clerk noticed differences in the spacing of the submitted documents. The court treated that matter more leniently because the person was not a lawyer, but required future documents to be submitted in printed form.
Separately, a state judge faced a federal lawsuit over allegations that she had used AI to outsource an entire ruling. The federal court held that she was protected by judicial immunity and could not be sued for those actions.
Sources: Tom's Hardware.