[HIGH] Filesystem MCP Path Traversal & Symlink Attack (Cymulate EscapeRoute)

Cymulate's EscapeRoute research (2025–2026) identified two flaws in the Anthropic Filesystem MCP server: a .startsWith() path-validation bypass enabling directory traversal, and a symlink-race attack allowing arbitrary file read/write including sensitive system files. Affected versions unverified — under review.