POST /registry/register accepted any URL string and persisted it as
the workspace's A2A endpoint — an attacker could register a workspace
with url=http://169.254.169.254/latest/meta-data/ and cause the platform
to proxy requests to the cloud metadata service when proxying A2A traffic.
Fix: validateAgentURL() helper rejects:
- empty URL
- non-http/https schemes (file://, ftp://, etc.)
- 169.254.0.0/16 link-local IPs (AWS/GCP/Azure IMDS endpoints)
Allows RFC-1918 private ranges (Docker networking uses 172.16-31.x.x).
Adds 12 unit tests covering valid Docker-internal URLs and all SSRF vectors.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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