Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.0.0 until 2.9.1, Addressable::IDNA.to_unicode can decode Punycode labels that contain bidirectional controls, zero-width characters, control characters, or other default-ignorable format characters. Addressable::URI#display_uri can consequently show a reordered or visually indistinguishable hostname even though host, normalized_host, and network connections use the original encoded hostname. The pure-Ruby backend accepts the full prohibited set, while the native libidn backend is affected from 2.5.2 for characters added after Unicode 3.2. This issue is fixed in version 2.9.1.