Web Application Security (Dagstuhl Seminar 18321).

This report documents the program and the outcomes of Dagstuhl Seminar 18321 "Web Application Security". In this third seminar on the topic, a healthy mix of academics, practitioners and representatives of all major browser vendors reflected on the last decade of web security research and discussed the upcoming security challenges for the Web platform. In addition, for the first time, the list of attendees included several members of the human factors in security community, to enable broadening the web security topic towards this important facet of application security.