--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -83,36 +83,32 @@
   background: #74BF43 url(chrome://browser/skin/update-badge.svg) no-repeat center;
   border-radius: 50%;
 }
 
 .panel-banner-item[notificationid^=update] {
   list-style-image: url(chrome://branding/content/icon16.png);
 }
 
-#PanelUI-menu-button[badge-status="fxa-needs-authentication"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
-  box-shadow: none;
-  filter: drop-shadow(0 1px 0 hsla(206, 50%, 10%, .15));
-}
-
+#PanelUI-menu-button[badge-status="addon-alert"] > .toolbarbutton-badge-stack > .toolbarbutton-badge,
 #PanelUI-menu-button[badge-status="fxa-needs-authentication"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
   height: 13px;
-  background: transparent url(chrome://browser/skin/warning.svg) no-repeat center;
+  background: url(chrome://browser/skin/warning.svg) center / contain no-repeat transparent;
+  box-shadow: none;
+  border-radius: 0;
+  /* Use the included fallbacks defined in the SVG file instead of inheriting from .toolbarbutton-1. */
+  -moz-context-properties: none;
 }
 
-#PanelUI-menu-button[badge-status="fxa-needs-authentication"] > .toolbarbutton-badge-stack > .toolbarbutton-badge:-moz-window-inactive {
-  filter: none;
+#PanelUI-menu-button[badge-status] > .toolbarbutton-badge-stack > .toolbarbutton-badge:-moz-window-inactive {
+  filter: grayscale(100%);
 }
 
-#PanelUI-menu-button[badge-status="addon-alert"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
-  height: 13px;
-  background: url(chrome://browser/skin/warning.svg) no-repeat center;
-}
-
-:root[lwt-popup-brighttext] #PanelUI-menu-button[badge-status="addon-alert"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
+#nav-bar[brighttext] #PanelUI-menu-button[badge-status="addon-alert"] > .toolbarbutton-badge-stack > .toolbarbutton-badge,
+#nav-bar[brighttext] #PanelUI-menu-button[badge-status="fxa-needs-authentication"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
   -moz-context-properties: fill, stroke;
   fill: #FFE900;
   stroke: transparent;
 }
 
 panelview {
   -moz-box-orient: vertical;
   -moz-box-flex: 1;