reap / rules / transport posture
Permissive CORS policy on agent endpoint
http-cors-wildcard ASI03 Identity and Privilege Abuse severity: high
What it detects
Wildcard or reflected CORS, confirmed via a real preflight; escalates when combined with credentialed cross-origin. ASI03.
Sends a foreign Origin header; flags Access-Control-Allow-Origin: *, escalating to High if combined with Access-Control-Allow-Credentials: true.
applies to any agent endpoint over HTTP
Why it matters
Permissive CORS lets an arbitrary web origin act as the agent from a victim's browser.
Example finding
HIGH http-cors-wildcard CONFIDENCE Permissive CORS policy on agent endpoint Server returns Access-Control-Allow-Origin: * — any web origin can call this endpoint from a browser context. Combined with Access-Control-Allow-Credentials: true, this allows credentialed cross-origin requests, which browsers should normally block.
from a scan of reap-range, bad target
Fix
Scope Access-Control-Allow-Origin to known first-party origins; never reflect an arbitrary Origin, and never combine * with credentialed requests.
On reap-range
| insecure target | bad/mcp (ACAO:* + credentials, seen on the POST response) · High |
| correct target | good/mcp sends no ACAO header |
Run only this check
reap -t https://your-host/mcp --authorized --include http-cors-wildcard
Not installed? Install REAP. Only scan systems you own or are authorised to test. Reference: docs/PROBES.md.