Russian phishing escalates; Turla malware evolves; GitHub AI agents at risk

This briefing reports multiple high-risk incidents: Russian intelligence phishing evolved to steal Signal backup recovery keys enabling persistent access to message histories; Turla APT has deployed StockStay malware against Ukrainian government and energy sectors; autonomous AI coding agents can be tricked into executing hidden malware from benign-looking GitHub repos; a Polymarket supply-chain compromise resulted in an estimated $3M customer loss; and attackers are impersonating companies via fraudulent OpenAI organization invites to collect sensitive information — the overall threat level is assessed as HIGH and remediation actions are recommended.