CVE-2020-15237

In Shrine before version 3.3.0, when using the derivation_endpoint plugin, it's possible for the attacker to use a timing attack to guess the signature of the derivation URL. The problem has been fixed by comparing sent and calculated signature in constant time, using Rack::Utils.secure_compare. Users using the derivation_endpoint plugin are urged to upgrade to Shrine 3.3.0 or greater. A possible workaround is provided in the linked advisory.