The UIProcess subsystem in WebKit as used in WebKitGTK through 2.23.90 and WebKitGTK+ through 2.22.6 and other products does not prevent the script dialog size from exceeding the web view size which allows remote attackers to cause a denial of service (Buffer Overflow) or possibly have unspecified other impact related to UIProcess/API/gtk/WebKitScriptDialogGtk.cpp UIProcess/API/gtk/WebKitScriptDialogImpl.cpp and UIProcess/API/gtk/WebKitWebViewGtk.cpp as demonstrated by GNOME Web (aka Epiphany).