An AGENTS.md planted in Downloads that can hijack coding agents, Meta’s 50 weekly conversions threshold, and a Brotli flaw that affects Node.js, Bun and .NET
Today’s 3 verified stories: Forever Security showed that an AGENTS.md planted in a user’s Downloads folder can hijack coding agents such as Codex and Claude Code, and the researchers say there is nothing to patch. Meta said that in its own analysis, ad sets under about 50 conversions a week cost about 28% more per purchase. The Brotli decoder flaw CVE-2026-111497 was disclosed on October 21, and its impact spread from Node.js to Bun, .NET and Python, with each product needing to update its own copy. Each story’s full analysis, sources and what it means for your business are on its own page.
An AGENTS.md planted in Downloads can hijack coding agents such as Codex and Claude Code
Security firm Forever Security caught a coding agent on a customer’s computer trying to install a malicious npm package, and the instruction came from an AGENTS.md file in the user’s Downloads folder. Agents read that file from the working directory on their own, so they follow the instructions in it. The researchers reproduced the attack on Codex and Claude Code; BleepingComputer reports a 90% success rate for Codex and code running in roughly half of tests for Claude Code, while Forever’s own report puts code execution within the same session at about a fifth of attempts. The researchers say there is nothing to patch. According to Forever’s data, about half of its customers run a coding agent inside Downloads. The advice is to start the agent in a specific project directory and to read any AGENTS.md you did not write before the agent sees it.
Meta says ad sets under about 50 weekly conversions cost about 28% more per purchase
Meta for Business published its peak-season guide on October 21, 2026, and Social Media Today and PPC Land reported on it October 25. In Meta’s own analysis, ad sets below roughly 50 conversions a week ran about 28% more expensive per purchase; that is Meta’s claim, not independent research. The guide describes each campaign as a brief handed to the ad auction and gives a formula for the most ad sets a budget can support: weekly budget ÷ (cost per result × 50). PPC Land notes that vendor reports cite lower thresholds, for example 25 purchases for Advantage+ shopping in 2026. This week’s advice is to hold the setup steady through October and measure with an A/B test or Conversion Lift study.
The Brotli decoder flaw behind a Node.js code execution bug also affects Bun, .NET and Python
Node.js shipped security releases on October 21, 2026 (22.23.4, 24.22.1 and 26.12.1) that close a write bug in its Brotli decoder, and it lists CVE-2026-111497 as high severity; Google published Brotli 1.0.10, 1.1.1 and 1.2.1 the same day. According to The Hacker News, affected software also includes Bun, Microsoft’s .NET, the Python packages Brotli and brotlicffi, and Envoy deployments where Brotli decompression is configured. Because every product carries its own copy of the decoder, one update does not cover them all, and after updating, services must be restarted and container images rebuilt. Severity scores differ: Google gives 9.2 on CVSS 4.0, Node.js says high, and Red Hat and Microsoft give 8.1.
The agenda moves fast, the system stays calm.
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