STJ opens investigation into prompt injection fraud in legal petitions
Brazil's Superior Court of Justice (STJ) launched a police inquiry and administrative investigation after technicians discovered hidden prompt injection commands in electronic legal petitions designed to manipulate the court's AI system. The court's AI system, STJ Logos, was already equipped with security mechanisms to block such attacks, and the court is identifying those responsible for potential sanctions and criminal liability.
What happened
The STJ determined on 20 May 2026 the opening of a police inquiry and administrative procedure to investigate attempts at procedural fraud using hidden prompt injection commands in petitions to manipulate the court's AI systems.
The practice involves inserting invisible instructions in judicial documents to attempt to influence responses generated by AI tools. Technical staff of the tribunal identified petitions containing such command injections in its case archive.
Reported impact
The attempts at manipulation were neutralized by the security layers of the STJ Logos system and will now be recorded in case files.
Index analysis
STJ Logos was developed with specific commands that prevent prompt injection attacks from succeeding, according to court president Herman Benjamin. The court is identifying those responsible to enable application of procedural sanctions and criminal and administrative accountability.
Classification
Sources and evidence
Sources not yet published
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