User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:18.104.22.168) Gecko/20060111 Firefox/22.214.171.124 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:126.96.36.199) Gecko/20060111 Firefox/188.8.131.52 When setting cookies, FF 184.108.40.206 often/sometimes adds a period "." in front of the domain. This usually causes problems especially when trying to unset the cookie. I saw TONS of potentially related forum questions but no bug report... Reproducible: Always Steps to Reproduce: 1. Clear all yahoo cookies from Firefox 2. goto http://mail.yahoo.com and accept cookie named "B" 3. view the cookie in Options Actual Results: The "Domain" of the cookie is set to ".yahoo.com" Expected Results: cookie domain should be set to "yahoo.com"
The period in the begining of the domain name indicates that the cookie is a subdomain-independent cookie. This allows you to login to mail.yahoo.com and have your cookie remain valid for yahoo.com. -> Invalid
it's menioned in RFC2109 : section 2 and 4.3.2