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Low reported severity Regulatory Action

Brazil's Supreme Federal Court reports its first hidden AI-directed command in an appeal petition; the rapporteur's vote applies a fine of two minimum wages

On 25 September 2026 Brazil's Supreme Federal Court (STF) announced that it had identified, for the first time, hidden commands in a petition intended to steer the court's artificial-intelligence systems toward a decision favourable to one party. According to the STF, the Maria Shield function of its internal Maria AI platform found instructions in white, reduced-size letters, with some words unusually fragmented, in an appeal (ARE 1608713) filed for a public servant whose appointment to a post at the Minas Gerais prosecution service had been annulled. The rapporteur's vote, presented to the First Panel in a virtual session beginning that day, records the detection, states that his office does not use AI to analyse cases, orders the episode certified in the record and communicated to the bar association (OAB) and the Federal Public Prosecutor's Office (MPF), and applies a fine of two minimum wages for breach of the duty of procedural loyalty (Code of Civil Procedure, article 77, IV). The vote names the lawyer responsible for the attempt; the record does not say whether the fine falls on the party or the lawyer, and the court states the attempt had no effect because the appeal had already been rejected on 19 August 2026.

AI system
Unidentified case-analysis tool
Occurred
3 Sept 2026 to 25 Sept 2026
Reported
25 September 2026
Event location
Brazil
What the AI did
Relation unknown
Reported harm
Legal HarmFinancial Loss
Whose AI use
An institution’s AI use
Setting
Justice · Work
Evidence
AI involvement supported · Causal attribution established · 2 sources, 1 underlying account
4 claims: 4 documented. 6 open questions
People reported harmed
At least 1 person

AI system as recorded: The STF's internal artificial-intelligence systems for case analysis, which the hidden commands targeted (the court does not name specific models); the commands were detected by Maria Shield, a function of the STF's Maria AI platform

What Happened

The appeal (ARE 1608713) was brought by a public servant whose appointment as an officer of the Minas Gerais prosecution service had been annulled in a dispute over the rules reserving competition places for Black candidates. The rapporteur had rejected the appeal on 19 August 2026 and the party filed an internal appeal against that decision. On 3 September 2026 the STF's Núcleo de Inteligência Artificial, part of the Secretariat-General of Technology and Innovation, informed the rapporteur's office that hidden instructions had been inserted in the petition: text in white, reduced-size letters, with some words fragmented in an unusual way, carrying arguments and commands intended to induce AI tools to admit and grant the appeal. The STF says the attempt was identified by Maria Shield, a function of its Maria platform that looks for potentially malicious patterns and content in filings, such as hidden commands aimed at AI systems. The rapporteur replied that his office does not use artificial intelligence to analyse cases or ground decisions, so the attempt had no effect on the appeal. In the vote presented to the First Panel in a virtual session beginning 25 September 2026, he recorded the detection, attributed the attempt to the lawyer who filed the appeal, ordered the episode certified in the record and communicated to the OAB and the MPF, held that the use of prompt injection breaches the duty of loyalty in article 77, IV, of the Code of Civil Procedure, denied the internal appeal and applied a fine of two minimum wages. The vote and the press note do not say whether the fine is imposed on the party or on the lawyer, and neither reports any response from the lawyer or the party.

Reported harm

The rapporteur's vote applies a fine of two minimum wages for breach of procedural loyalty and orders the episode communicated to the bar association for a possible disciplinary infraction and to federal prosecutors to assess a possible crime; the STF press note reports the fine as applied.

Outcome

Ongoing

Rapporteur's vote in ARE 1608713 (second internal appeal), Minister Cristiano Zanin, First Panel virtual session beginning 25 September 2026: the internal appeal is denied; a fine of two minimum wages is applied for violation of article 77, IV, of the Code of Civil Procedure; the episode is certified in the record and communicated to the Ordem dos Advogados do Brasil (possible ethical-disciplinary infraction) and to the Federal Public Prosecutor's Office (possible crime, if it sees fit). The STF press note describes the fine as applied. Whether the panel concluded the judgment, who pays the fine, and the outcome of the OAB and MPF communications are not reported.

What remains unknown

  • Whether the fine of two minimum wages is imposed on the appellant, on the lawyer, or jointly.
  • Whether the First Panel concluded the virtual judgment and confirmed the vote.
  • Who inserted the hidden text and how; no response from the lawyer or the appellant is reported.
  • Which AI systems the STF uses for case analysis and whether any processed the petition before the detection.
  • How the Maria Shield function detects such content.
  • The outcome of the communications to the OAB and the MPF.

What the evidence supports

AI involvement: supported. The STF press note and the rapporteur's vote record that the court's AI unit detected 'prompt injection' in the petition: hidden instructions in white, reduced-size letters intended to direct the court's AI systems toward admitting and granting the appeal. The targeted AI is the STF's internal system for case analysis, which the court does not name by model; the detection is attributed to Maria Shield, a function of the court's Maria platform, which the press note describes as an AI system developed by the STF to support staff in case analysis and document production; the sources do not say how the Maria Shield function detects such content. No source reports any AI system processing or acting on the hidden text: the rapporteur states his office does not use AI and that the appeal had already been rejected. The harm is the court's response to the attempt (fine and communications), so no relation describing the AI system's own action toward the lawyer is established (unknown).

4 claims: 4 documented. What the statuses mean

Documented In his vote on the second internal appeal in ARE 1608713, presented to the First Panel in a virtual session beginning 25 September 2026, the rapporteur denied the appeal and applied a fine of two minimum wages for violation of article 77, IV, of the Code of Civil Procedure, holding that the use of prompt injection breaches the duty of procedural loyalty.

Causal attribution. The fine and its ground are established by the vote itself; the press note restates them. Whether the fine falls on the party or the lawyer is not stated.

Documented The vote names the lawyer who filed the appeal as the author of the attempt to covertly direct the STF's AI systems, and orders the episode certified in the record and communicated to the Ordem dos Advogados do Brasil, for a possible ethical-disciplinary infraction, and to the Federal Public Prosecutor's Office, to assess a possible crime if it sees fit.

Causal attribution. Established by the vote; the outcome of either communication is not reported.

  • noticias-stf-wp-prd.s3.sa-east-1.amazonaws.com(opens in new tab) supports · Portuguese
    'a comunicação à Ordem dos Advogados do'; 'Brasil para que verifique eventual infração ético-disciplinar por parte do'; 'apurar eventual prática de crime, se entender cabível (doc. 53, p. 3)'
  • noticias.stf.jus.br(opens in new tab) supports · Portuguese
    'determinou que o fato seja comunicado à Ordem dos Advogados do Brasil (OAB), para análise de eventual infração ético-disciplinar, e ao Ministério Público Federal (MPF), para apuração de eventual prática de crime'
Documented On 3 September 2026 the STF's AI unit informed the rapporteur's office that the petition contained hidden instructions, in white, reduced-size letters with some words unusually fragmented, carrying arguments and commands intended to induce AI tools to admit and grant the appeal; the STF attributes the detection to Maria Shield, a function of its Maria AI platform.

Causal attribution. The press note and the vote document the detection and its description; neither says how the text was inserted or whether any AI system processed it.

  • noticias.stf.jus.br(opens in new tab) supports · Portuguese
    'foi comunicado da tentativa de burla processual em 3 de setembro pelo Núcleo de Inteligência Artificial'; 'instruções ocultas, em letras brancas e de tamanho reduzido, com argumentos e comandos destinados a induzir ferramentas de IA a conhecer e dar provimento ao recurso'; 'A tentativa foi identificada pela Maria Shield, uma das funcionalidades da plataforma Maria'
  • noticias-stf-wp-prd.s3.sa-east-1.amazonaws.com(opens in new tab) supports · Portuguese
    'detectou neste RE 1.608.713 o uso de “prompt injection”, cuja técnica é'; 'de direcionar, de forma oculta, os sistemas de inteligência artificial do'
Documented The rapporteur stated that his office does not use artificial intelligence to analyse cases or ground decisions and that the appeal had already been rejected on 19 August 2026, so the attempt had no effect on the decision.

Causal attribution. The rapporteur's own statement, recorded in the vote and the press note.

Sources

2 sources inspected, from 1 underlying account. Sources that repeat one account do not corroborate each other.

How the sources were read, and where the events happened

Read live in Portuguese on 2026-10-07 (STF news portal, 25 September 2026). Translation by the research agent (an AI). Applies to s1.

Read in Portuguese on 2026-10-07 from the PDF the STF press note links (rapporteur's vote, 6 pages, text layer extracted). Translation by the research agent (an AI). Applies to s2.

Event countries: Brazil. Affected-person countries: Unknown. Court countries: Brazil.

The petition was filed in ARE 1608713 before Brazil's Supreme Federal Court, which detected the commands and whose rapporteur issued the vote in Brasília. The appellant's post and the lawyer's bar registration are in Minas Gerais, Brazil; no source states where the lawyer lives.

Reviewed for publication 2026-10-07: Published as a consequential-response case: the STF's own press note and the rapporteur's vote, both read directly, record that hidden commands aimed at the court's AI systems were found in an appeal petition and that the court responded with a fine, certification in the record and communications to the bar and prosecutors naming the lawyer. The two sources form one chain (the court's own record), so the claims rest on the court record and are marked documented. No AI system is reported to have processed the text, so the relation is unknown. The lawyer and the appellant are not named.

People described

A lawyer registered with the Minas Gerais section of the Brazilian bar who filed the appeal for a public servant; named in the vote, not named here

People reported harmed in this case

At least 1 person

0 AI participants · 1 other person harmed

At least one person: the lawyer whom the vote names as the author of the attempt and who is the subject of the OAB and MPF communications. The vote applies a fine of two minimum wages without naming who pays it (party or lawyer), so the person bearing the fine may be a second harmed person and is not counted. Counted under other people because the AI involved was the court's, not a tool the lawyer is reported to have used.

Counted once within this case. The same person may appear in other cases. This count does not establish AI causation.

Tags

#justice#legal-profession#sanction#prompt-injection#court-ai#brazil#stf#portuguese-language

Cite this case

Compiled per our published methodology: verification statuses, sourcing standards, and corrections process.

APA

NOPE. (2026). Brazil's Supreme Federal Court reports its first hidden AI-directed command in an appeal petition; the rapporteur's vote applies a fine of two minimum wages. AI incidents. https://nope.net/incidents/2026-brazil-stf-first-hidden-ai-prompt-in-appeal-petition-fine-two-minimum-wages

BibTeX

@misc{2026_brazil_stf_first_hidden_ai_prompt_in_appeal_petition_fine_two_minimum_wages,
  title = {Brazil's Supreme Federal Court reports its first hidden AI-directed command in an appeal petition; the rapporteur's vote applies a fine of two minimum wages},
  author = {NOPE},
  year = {2026},
  howpublished = {AI incidents},
  url = {https://nope.net/incidents/2026-brazil-stf-first-hidden-ai-prompt-in-appeal-petition-fine-two-minimum-wages}
}

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