fix https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909626

platform/webext/manifest.json

@@ -93,7 +93,8 @@
     "default_icon": {
       "16": "img/ublock.svg",
       "48": "img/ublock.svg"
-    }
+    },
+    "open_at_install": false
   },
   "storage": {
     "managed_schema": "managed_storage.json"

tools/make-webext-meta.py

@@ -27,6 +27,12 @@ if match:
     webext_manifest['name'] += ' development build'
     webext_manifest['short_name'] += ' dev build'
     webext_manifest['browser_action']['default_title'] += ' dev build'
+else:
+    # https://bugzilla.mozilla.org/show_bug.cgi?id=1459007
+    # By design Firefox opens the sidebar with new installation of
+    # uBO when sidebar_action is present in the manifest.
+    # Remove sidebarAction support for stable release of uBO.
+    del webext_manifest['sidebar_action']
 
 with open(webext_manifest_file, mode='w', encoding='utf-8') as f2:
     json.dump(webext_manifest, f2, indent=2, separators=(',', ': '), sort_keys=True)