Advisories for Gem/Pay package

Pay::Webhooks::PaddleBillingController#valid_signature? (app/controllers/pay/webhooks/paddle_billing_controller.rb) verifies the Paddle Billing webhook signature by computing OpenSSL::HMAC.hexdigest(…) and comparing it to the attacker-supplied header value using Ruby's String#==. Ruby's == is non-constant-time — it returns as soon as the first byte mismatches — and exposes a per-byte timing side channel on the webhook signature verification path. The canonical mitigation is to use a constant-time primitive (OpenSSL.fixed_length_secure_compare / ActiveSupport::SecurityUtils.secure_compare).

Pay is a payments engine for Ruby on Rails 6.0 and higher. In versions prior to 6.3.2 a payments info page of Pay is susceptible to reflected Cross-site scripting. An attacker could create a working URL that renders a javascript link to a user on a Rails application that integrates Pay. This URL could be distributed via email to specifically target certain individuals. If the targeted application contains a functionality …