docs(cors): Security section on wildcard origin + credentials (#277)#418
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Upstream echo#2400 asked for the docs to explain the danger of combining a wildcard origin with AllowCredentials, and the maintainer asked for a security block on echo.labstack.com. The page only had a one-line caution that didn't explain the behaviour or v5's enforcement. Expand it into a "Security" section that explains: - the danger: wildcard origin + AllowCredentials:true reflects any Origin back, enabling credentialed cross-origin attacks; - v5's enforcement: CORS / CORSWithConfig panic and ToMiddleware() returns an error rather than building an insecure middleware; - the safe pattern (explicit origins) and UnsafeAllowOriginFunc for dynamic validation. Applied across all five locales (translated prose, identical code block). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Closes #277 (which tracked upstream echo#2400).
Background
echo#2400 reported that a wildcard origin +
AllowCredentials: truereflects any request'sOriginback inAccess-Control-Allow-Origin— a cross-origin attack vector. The maintainer's resolution note: "we need to add a security block to echo.labstack.com." The CORS page only had a terse one-line caution.Change
Replaces that caution with a proper Security section that explains:
*+AllowCredentials: truereflects anyOrigin, allowing credentialed cross-origin requests from any site (links to the PortSwigger write-up).CORSandCORSWithConfigpanic, andCORSConfig.ToMiddleware()returns an error, instead of building the insecure middleware (verified against echo v5middleware/cors.go).UnsafeAllowOriginFuncfor dynamic validation, with a caution about hostile subdomains.Applied across all 5 locales (translated prose, identical code block).
Verification
toMiddlewareOrPanicand the"* as allowed origin and AllowCredentials=true is insecure and not allowed"error.Closes #277
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