Last Week In AppSec for 08. July 2025

This report highlights three application-security issues: (1) a 0-click data-leakage path in Anthropic's deprecated Slack MCP server that can leak secrets via prompt injection and Slack link expansion; (2) a verification-spoofing defect in IDE extension handling (VSCode, IntelliJ, Cursor) that lets malicious extensions appear as coming from verified publishers when installed outside marketplaces; and (3) a Next.js CVE-2025-49826 race-condition bug causing incorrect HTTP 204 responses to be cached and produce a denial-of-service, with vendor fixes or mitigations noted for each.