diff --git a/static/js/app.js b/static/js/app.js
index 522f763..e8f8d58 100644
--- a/static/js/app.js
+++ b/static/js/app.js
@@ -2199,6 +2199,13 @@ function bookFileSelected(input) {
 
 function initBookDropZone() {
   const zone = $('book-drop-zone');
+
+  // Prevent Firefox from opening dragged files when dropped outside the zone
+  document.addEventListener('dragover', e => e.preventDefault());
+  document.addEventListener('drop', e => {
+    if (!zone || !zone.contains(e.target)) e.preventDefault();
+  });
+
   if (!zone) return;
 
   zone.addEventListener('dragover', e => {