A Brazilian labor court has sanctioned and fined two lawyers after discovering that they deliberately hid a prompt-injection command inside a court filing, according to a report by JetStream Security. The case originated from an employment claim filed with the 3rd Labor Court of Parauapebas, in the state of Pará, Brazil.
The lawyers knew that Brazilian courts use an AI system to review filings, and they embedded an instruction designed to make that system treat their case leniently. The court fined the two law firms that jointly filed the tainted petition 10% of the claim's value. The claim was R$842,000, which works out to approximately $16,000.
How the prompt injection was hidden
During the judge's review of the petition via Galileu, the generative AI tool used nationwide by Brazil's National Justice Council, the system detected text set in white font on a white background, invisible to anyone reading the document normally. Once the font color was changed, the hidden instruction became readable: it told the AI to respond to the petition superficially and not to challenge the documents, regardless of any other command.
Brazilian news outlet G1 reported that Galileu raised an alert and automatically blocked processing of the suspicious content once the interference attempt was identified.
Why the court called it an attack on justice
The court determined that the lawyers intended to make any AI system used by the opposing party or by the court itself generate a superficial response or a biased draft judgment, harming the defendant and the administration of justice. It treated the conduct as an act undermining the dignity of justice.
The sanction was based on procedural good-faith obligations in Article 5 of the Brazilian Civil Procedure Code, including duties of loyalty, truthfulness and respect for institutions. Article 77 of the Code prohibits parties and counsel from obstructing judicial processes, including a duty not to introduce illegal innovations into the factual or legal state of the proceeding and not to act in a way that makes judicial activity difficult.
