This problem occurs because of how ISA Server 2006 parses cookie content when ISA Server performs Forms-based authentication.
When you use Forms-based authentication, ISA Server must parse the cookie content to extract the Forms-based authentication cookie. ISA Server requires the Forms-based authentication cookie to authenticate the user. To parse the cookie content, the parsing code in ISA Server looks for a semicolon or a comma to separate individual cookies.
Note According to Request For Comment (RFC) 2965 Section 3.3.4, cookies may be separated by using either a semicolon or a comma. A cookie may have the following format:
cookie = "Cookie:" cookie-version 1*((";" | ",") cookie-value)
After ISA Server extracts the Forms-based authentication cookie, it rebuilds the cookie content. During this process, ISA Server separates the individual cookies by using a semicolon character together with a space.
Note ISA Server uses a semicolon to separate individual cookies regardless of how the cookies were separated originally.
Because of how the cookie parsing code works in ISA Server, any comma in the cookie content is replaced by a semicolon. Therefore, if a Web application requires commas in the cookie content, the Web application may not work.
Important A semicolon or a comma may be used as a delimiter in cookie content. Therefore, we recommend that a Web application does not use a semicolon or a comma as part of cookie content.