Firefox: Files in menu items (such as explorer) are opened on mouseup, not onclick

Hi!

When I select a line in the editor I often start my selection from the end of the line, pressing the mouse left button and go to the beginning of the line and release the mouse button. However I go further than the beginning of the line to be quick and my cursor is on the left panel (ex: Explorer).

When I release the mouse button this triggers a mouseup event in the panel, for example an extension, which causes it to open in the editor (thus switching the active file being edited).

Example with this code:

/**
 * @class mynamespace.Component class
 */
mynamespace.Component = function () {
	
};

/**
 * Fires a <i>onComponentTitleChanged</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireTitleChanged = function () {
	this._listeners.forEach(l => {
		if (l.onComponentTitleChanged) {
			l.onComponentTitleChanged(this, this._title);
		}
	});
};

/**
 * Fires a <i>onComponentIconChanged</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireIconChanged = function () {
	this._listeners.forEach(l => {
		if (l.onComponentIconChanged) {
			l.onComponentIconChanged(this, this._icon);
		}
	});
};

/**
 * Fires a <i>onComponentResized</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireResized = function () {
	this._listeners.forEach(l => {
		if (l.onComponentResized) {
			l.onComponentResized(this);
		}
	});
};

/**
 * Fires a <i>onComponentMinimized</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireMinimized = function () {
	this._listeners.forEach(l => {
		if (l.onComponentMinimized) {
			l.onComponentMinimized(this, this._isMinimized);
		}
	});
};

/**
 * Fires a <i>onComponentMaximized</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireMaximized = function () {
	this._listeners.forEach(l => {
		if (l.onComponentMaximized) {
			l.onComponentMaximized(this, this._isMaximized);
		}
	});
};

/**
 * Fires a <i>onComponentClosed</i> event on all registered listeners.
 * @private
 */
mynamespace.Component.prototype._fireClosed = function () {
	for (var i = this._listeners.length - 1; i >= 0; --i) {
		var l = this._listeners[i];
		if (l.onComponentClosed) {
			l.onComponentClosed(this);
		}
	}
};

See this gif: I select some code then release the mouse button over the "Jupyter" item in the extensions panel, which opens it on the right side.

This only happens in vscode.dev (or other web versions of it), not the desktop vscode app.

(Initially opened in https://github.com/gitpod-io/gitpod/issues/10559)

Version: 1.77.3 Commit: 704ed70d4fd1c6bd6342c436f1ede30d1cff4710 User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/113.0 Embedder: vscode.dev