diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index 482fc4b..c23423c 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -3199,6 +3199,11 @@
     border-radius: 0 !important;
   }
 }
+@supports -moz-bool-pref("userChrome.rounding.square_infobox") {
+  #sanitizeEverythingWarningBox {
+    border-radius: 0 !important;
+  }
+}
 @supports -moz-bool-pref("userChrome.rounding.square_toolbar") {
   :root {
     --uc-rounding-toolbar: 0;
diff --git a/src/rounding/_square.scss b/src/rounding/_square.scss
index 8151c24..5722402 100644
--- a/src/rounding/_square.scss
+++ b/src/rounding/_square.scss
@@ -65,6 +65,12 @@
   }
 }
 
+@include Option("userChrome.rounding.square_infobox") {
+  #sanitizeEverythingWarningBox {
+    border-radius: 0 !important;
+  }
+}
+
 @include Option("userChrome.rounding.square_toolbar") {
   :root {
     --uc-rounding-toolbar: 0;