[wp-trac] [WordPress Trac] #53529: Block based widget admin screen causes a NS_ERROR_FAILURE error in Firefox

[WordPress Trac]

#53529: Block based widget admin screen causes a NS_ERROR_FAILURE error in Firefox
--------------------------+-----------------------------
 Reporter:  walterebert   |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Widgets       |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 On the new widget screen the following error occurs in Firefox 89.0.2 in
 the console, when loading the page:

 {{{
 Uncaught
 Exception { name: "NS_ERROR_FAILURE", message: "", result: 2147500037,
 filename: "http://wpbeta.localhost/wp-admin/widgets.php?legacy-widget-p
 …gacy-widget-preview%5Binstance%5D%5Braw%5D%5Bnav_menu%5D=181",
 lineNumber: 14, columnNumber: 0, data: null, stack:
 "t.supports[o[r]]<@http://wpbeta.localhost/wp-admin/widgets.php?legacy-
 widget-preview%5BidBase%5D=nav_menu&legacy-widget-
 preview%5Binstance%5D%5Bencoded%5D=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9
 &legacy-widget-
 preview%5Binstance%5D%5Bhash%5D=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-
 preview%5Binstance%5D%5Braw%5D%5Bnav_menu%5D=181:14:628\n at http://wpbeta.localhost
 /wp-admin/widgets.php?legacy-widget-preview%5BidBase%5D=nav_menu&legacy-
 widget-
 preview%5Binstance%5D%5Bencoded%5D=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9
 &legacy-widget-
 preview%5Binstance%5D%5Bhash%5D=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-
 preview%5Binstance%5D%5Braw%5D%5Bnav_menu%5D=181:14:1102\n at http://wpbeta.localhost
 /wp-admin/widgets.php?legacy-widget-preview%5BidBase%5D=nav_menu&legacy-
 widget-
 preview%5Binstance%5D%5Bencoded%5D=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9
 &legacy-widget-
 preview%5Binstance%5D%5Bhash%5D=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-preview%5Binstance%5D%5Braw%5D%5Bnav_menu%5D=181:14:1779\n" }
 widgets.php:14
     t.supports[o[r]]< http://wpbeta.localhost/wp-admin/widgets.php?legacy-
 widget-preview[idBase]=nav_menu&legacy-widget-
 preview[instance][encoded]=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9&legacy-
 widget-preview[instance][hash]=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-preview[instance][raw][nav_menu]=181:14
     <anonymous> http://wpbeta.localhost/wp-admin/widgets.php?legacy-
 widget-preview[idBase]=nav_menu&legacy-widget-
 preview[instance][encoded]=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9&legacy-
 widget-preview[instance][hash]=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-preview[instance][raw][nav_menu]=181:14
     <anonymous> http://wpbeta.localhost/wp-admin/widgets.php?legacy-
 widget-preview[idBase]=nav_menu&legacy-widget-
 preview[instance][encoded]=YToxOntzOjg6Im5hdl9tZW51IjtpOjE4MTt9&legacy-
 widget-preview[instance][hash]=2421412fbc986f068f1a768eb85295f7&legacy-
 widget-preview[instance][raw][nav_menu]=181:14
 }}}

 Tested this in WordPress 5.8-beta4-51244. It seems to be related to the
 use of a canvas element in an iframe. Also see
 https://bugzilla.mozilla.org/show_bug.cgi?id=941146.

 This errors does not occur in other browsers.

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Ticket URL: <https://core.trac.wordpress.org/ticket/53529>
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