If you have Audience Targeting deployed, every time the "extend session" event is called, you will see a 404 error in browser console.
Steps to reproduce
1.- Start Liferay 6.2
1.1.- To speed up the reproduction process you can define session-timeout in you application server to 1, and session.timeout.auto.extend=true in portal-ext.properties.
2.- Deploy Audience Targeting
3.- Open the browser console and wait until the extend session event is called.
The "extend session" event returns 200
The "extend session" event returns 404