dingtalk.py: The session_webhook URL from incoming DingTalk messages is POSTed to
without any origin validation (line 290), enabling SSRF attacks via crafted webhook
URLs (e.g. http://169.254.169.254/ to reach cloud metadata). Add a regex check
that only accepts the official DingTalk API origin (https://api.dingtalk.com/).
Also cap _session_webhooks dict at 500 entries with FIFO eviction to prevent
unbounded memory growth from long-running gateway instances.
api_server.py: The X-Hermes-Session-Id request header is accepted and echoed back
into response headers (lines 675, 697) without sanitization. A session ID
containing \r\n enables HTTP response splitting / header injection. Add a check
that rejects session IDs containing control characters (\r, \n, \x00).
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
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