What Happened
Cybersecurity researchers have discovered a malicious NuGet package that masquerades as a C# software development kit for Sicoob, one of Brazil's largest cooperative financial systems, to siphon client IDs and PFX certificates. According to Socket, versions 2.0.0 through 2.0.4 of "Sicoob.Sdk" contain functionality to exfiltrate sensitive information, including PFX certificates that are used to
Why It Matters
The report describes a malicious NuGet package, Sicoob.Sdk versions 2.0.0 through 2.0.4, that masquerades as a legitimate SDK and exfiltrates client IDs, PFX passwords, and PFX certificate data through Sentry telemetry.[1][3] It also captures some Boleto API responses, which can expose payment and transaction details.[1][3] CyberSE.AI analysis: this is a high-severity supply-chain data leakage incident because stolen certificate material and credentials could enable impersonation of banking integrations and unauthorized financial API access.
CyberSE Analysis
This signal maps to data leakage. Organizations using AI agents, LLM APIs, SaaS integrations, or sensitive data workflows should review whether this class of issue could create unauthorized tool execution, data leakage, weak approval gates, or unmanaged supply-chain exposure.
Recommended Actions
- Restrict AI agent tool permissions and production write paths.
- Review sensitive data access across prompts, logs, embeddings, memory, and SaaS integrations.
- Add human approval workflows for high-impact or state-changing actions.
- Run prompt injection and indirect prompt injection tests against affected workflows.
- Document the owner, control gap, and remediation deadline for this risk class.
Source
https://thehackernews.com/2026/05/malicious-sicoob-nuget-steals-banking.html