Hello,

On one of my browsers, I suddenly became unable to log into limesurvey, and trying to answer a survey invariably led, with that same browser, to an error message stating that my session had expired.

I found out that on that browser, I had a PHPSESSID cookie set by my self-hosted limesurvey instance (let's say that its domain name is limesurvey.mydomain.org), and another PHPSESSID cookie set by another website, but associated with the higher level domain name "mydomain.org", and having "/" as its path.

When accessing my limesurvey instance after visiting the other website, the browser sends both cookies, which is the expected behaviour per RFC6265 (https://tools.ietf.org/html/rfc6265).

After deleting the PHPSESSID cookie associated with the "mydomain.org" domain, the behaviour of limesurvey is back to normal.

So, it looks like limesurvey is mistaking one PHPSESSID cookie for the other. This might be due to the fact that it is not expecting more than 1 PHPSESSID cookie to be sent.

In §4.2.2, RFC6265 states:

"Although cookies are serialized linearly in the Cookie header, servers SHOULD NOT rely upon the serialization order. In particular, if the Cookie header contains two cookies with the same name (e.g., that were set with different Path or Domain attributes), servers SHOULD NOT rely upon the order in which these cookies appear in the header."

It looks like limesurvey's behaviour is somewhat disturbed by the presence of 2 cookies with the same name.