From 88e88957ded6f7183676b6b6b63a0042fcafe9ee Mon Sep 17 00:00:00 2001
From: Alex Yang <himself65@outlook.com>
Date: Thu, 16 Jul 2026 01:16:43 -0700
Subject: [PATCH] fix(core): ignore synthetic mousemove events without
 coordinates in side menu
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A mousemove created via `new Event("mousemove")` (e.g. dispatched by a
browser extension) is a plain Event with no `clientX`/`clientY`. The
side menu's document-level listener stored the resulting `undefined`
coordinates, and `document.elementsFromPoint()` then threw
"TypeError: The provided double value is non-finite" in
`getBlockFromCoords` — including on read-only editors, since the
`isEditable` check only runs after the coordinate lookup.

Ignore mousemove events whose coordinates are not finite numbers.
---
 packages/core/src/extensions/SideMenu/SideMenu.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/packages/core/src/extensions/SideMenu/SideMenu.ts b/packages/core/src/extensions/SideMenu/SideMenu.ts
index 76d1983476..e5572c004c 100644
--- a/packages/core/src/extensions/SideMenu/SideMenu.ts
+++ b/packages/core/src/extensions/SideMenu/SideMenu.ts
@@ -600,6 +600,14 @@ export class SideMenuView<
       return;
     }
 
+    // Synthetic mousemove events created via `new Event("mousemove")` (e.g.
+    // dispatched by browser extensions) have no `clientX`/`clientY`, which
+    // would make `elementsFromPoint` throw on the resulting non-finite
+    // coordinates.
+    if (!Number.isFinite(event.clientX) || !Number.isFinite(event.clientY)) {
+      return;
+    }
+
     this.mousePos = { x: event.clientX, y: event.clientY };
 
     // We want the full area of the editor to check if the cursor is hovering