Issue #19153 has been updated by hsbt (Hiroshi SHIBATA). FYI: https://github.com/ruby/cgi/pull/29#issuecomment-1328487556 I released [cgi-0.3.6](https://github.com/ruby/cgi/releases/tag/v0.3.6) for this issue. Can you try it with adding `"cgi", ">= 0.3.6"` in your Gemfile. ---------------------------------------- Bug #19153: Since 2.7.7 CGI::Cookie raises ArgumentError when cookie domains is prefixed with a dot https://bugs.ruby-lang.org/issues/19153#change-100286 * Author: cpinto (Celso Pinto) * Status: Open * Priority: Normal * ruby -v: ruby 2.7.7p221 (2022-11-24 revision 168ec2b1e5) [arm64-darwin22] * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN ---------------------------------------- The rspec tests of our Rails app started failing with an ArgumentError after upgrading to 2.7.7. On inspection, the issue seems to be caused by CGI::Cookie.domain=: ``` def domain=(str) if str and ((str = str.b).bytesize > 255 or !DOMAIN_VALUE_RE.match?(str)) raise ArgumentError, "invalid domain: #{str.dump}" end @domain = str end ``` Setting a breakpoint: 0> str => ".example.com" 0> DOMAIN_VALUE_RE => /\A(?<label>(?!-)[-A-Za-z0-9]+(?<!-))(?:\.\g<label>)*\z/ 0> DOMAIN_VALUE_RE.match?(str) => false 0> DOMAIN_VALUE_RE.match?('example.com') => true -- https://bugs.ruby-lang.org/