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Digest · Thursday

Security digest: September 17, 2026

1 editorial brief and 9 critical advisories.

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Take stock

  • Check exposure: Plugin4Shell. Teams that install third-party plugins in GitHub Copilot or Gemini CLI, run Claude Code older than 2.1.179 or Codex older than 0.146.0, or run an internal plugin marketplace on Bitbucket or a self-hosted git server.
  • Composer (PHP): 4 critical advisories (cakephp/database, cakephp/cakephp, getgrav/grav, chamilo/chamilo-lms). Check with composer audit.
  • Go: 3 critical advisories (github.com/rabbitmq/amqp091-go). Check with govulncheck ./....
  • NuGet: 1 critical advisory (Marten). Check with dotnet list package --vulnerable --include-transitive.
  • npm: 1 critical advisory (@vendure/core). Check with npm audit (or: npm ls <package>).
  • None of it touches your stack? Then there is nothing to do today. That is a result, not a failure to read carefully.

Editorial briefs

Check exposure

· AI agent security · CVE-2026-86063

Plugin4Shell: Plugin Pin Bypass in AI Coding Agents

Claude Code and Codex users on current versions are fixed; the real exposure is Copilot or Gemini CLI plugins that auto-update from repositories hosted outside GitHub.

Must act: Teams that install third-party plugins in GitHub Copilot or Gemini CLI, run Claude Code older than 2.1.179 or Codex older than 0.146.0, or run an internal plugin marketplace on Bitbucket or a self-hosted git server.

Can relax: Claude Code and Codex users on auto-update with no Copilot or Gemini CLI plugins, and anyone who installs no third-party agent plugins at all.

  1. Confirm versions: claude --version should report 2.1.179 or later and codex --version 0.146.0 or later; update with claude update or npm i -g @openai/codex@latest.
  2. Inventory installed agent plugins and the git host behind each plugin and marketplace; flag anything on Bitbucket or a self-hosted server.
  3. For Copilot, disable automatic plugin updates where you can and remove plugins sourced from hosts that allow SHA-shaped branch names.

Read the brief →

Known exploited (CISA KEV) 0

Added to CISA’s catalog on this day: confirmed exploitation in the wild. Due date = CISA’s deadline for US federal agencies.

None.

Critical advisories by ecosystem 9

GitHub-reviewed advisories rated critical, published this day (Pacific time).

Composer (PHP) 4

Check: composer audit

Go 3

Check: govulncheck ./...

npm 1

Check: npm audit (or: npm ls <package>)

NuGet 1

Check: dotnet list package --vulnerable --include-transitive