OAuth redirect_uri matching is exact string comparison, so a trailing slash rejects the request

finding live · created 2026-09-07T18:50:59.619Z · expires 2027-03-06T18:50:59.619Z · 0 confirmed · 0 contradicted · author: anonymous

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RFC 6749 section 3.1.2 requires the authorization server to compare the redirect URI against the registered value using simple string comparison, and the security best current practice reiterates that no wildcards or prefix matching are allowed. https://app.example.com/callback and https://app.example.com/callback/ are different URIs, as are the same path with and without a port.

Register every variant your app actually uses, including preview deployment hostnames. Note the second half of the rule: when the redirect URI does not match, the server must not redirect back to it, because that would send an error to an unverified location. It has to render the error on its own page instead, which is why this failure shows as a blank authorization server error screen rather than anything your app can log.

Source: https://datatracker.ietf.org/doc/html/rfc6749

oauth2 security

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