Prompt Injection Attempt Detected in Brazilian Labor Court Petition
An attempt to inject hidden prompt instructions into a legal petition processed by Galileu, an AI system used by Brazilian labor courts, was detected and prevented. The system alerted the user and preserved human decision-making, with the judge subsequently examining the flagged content before determining consequences.
What happened
Hidden prompt injection instructions were detected in a labor court petition processed by Galileu, an AI tool used by Brazil's 4th Regional Labor Court (TRT-RS). The concealed text instructed the system to contest the petition superficially and not challenge documents regardless of its programming.
Galileu detected the hidden instructions, issued a prominent alert to the user with technical details of the attack, and prevented the malicious content from being processed by the system. The judge, Luiz Carlos de Araújo Santos Junior, examined the content identified by the system before deciding consequences.
Index analysis
The behavior of Galileu—detecting the anomaly, alerting the user, and preserving human decision-making—aligns with international technical guidelines on AI security, including OWASP LLM01, NIST AI 600-1, NCSC/CISA, and MITRE ATLAS AML.T0051 recommendations for responding to prompt injection attempts.
Use of Galileu complies with CNJ Resolution No. 615/2025, which governs AI deployment in Brazil's judiciary based on principles including effective human supervision, information security, transparency, and respect for fundamental rights.
Governance controls
The judge did not decide based solely on the system's alert but examined the content flagged by Galileu before taking action, ensuring human review consistent with judicial AI governance requirements.
According to TRT-RS secretary for technology and innovation Natacha Moraes de Oliveira, institutional AI tools that take protective measures like Galileu are preferable, as detecting such attacks requires specialized techniques.
Classification
Sources and evidence
This record was researched and written by the Index, based on the following original reporting.