Prevent dropping files onto captcha causing navigation to the file.

src/General/css/style.css

@@ -1267,6 +1267,11 @@ input.field.tripped:not(:hover):not(:focus) {
   width: 100%;
 }
 
+/* Prevent dragging files into captcha */
+:root.dragging iframe {
+  pointer-events: none;
+}
+
 /* File Input, Submit Button */
 #file-n-submit {
   display: -webkit-flex;

src/Posting/QR.coffee

@@ -75,6 +75,8 @@ QR =
     $.on d, 'dragover',           QR.dragOver
     $.on d, 'drop',               QR.dropFile
     $.on d, 'dragstart dragend',  QR.drag
+    $.on d, 'dragenter',          QR.dragEnter
+    $.on d, 'dragleave',          QR.dragLeave
 
     $.on d, 'IndexRefresh', QR.generatePostableThreadsList
     $.on d, 'ThreadUpdate', QR.statusCheck
@@ -315,12 +317,25 @@ QR =
     e.dataTransfer.dropEffect = 'copy' # cursor feedback
 
   dropFile: (e) ->
+    delete QR.dragTarget
+    $.rmClass doc, 'dragging'
+
     # Let it only handle files from the desktop.
     return unless e.dataTransfer.files.length
+
     e.preventDefault()
     QR.open()
     QR.handleFiles e.dataTransfer.files
 
+  dragEnter: (e) ->
+    QR.dragTarget = e.target
+    $.addClass doc, 'dragging'
+
+  dragLeave: (e) ->
+    if QR.dragTarget is e.target
+      delete QR.dragTarget
+      $.rmClass doc, 'dragging'
+
   paste: (e) ->
     return unless e.clipboardData.items
     files = []