9d69f8ea_JSErrorReport___Mozilla___MDN__Description
[Name] isMuted [Type] bool [Description] 
The Web Platform allows scripts to be loaded from arbitrary cross-origin sources. This allows an attack by which a malicious website loads a sensitive file (say, a bank statement) cross-origin (using the user's cookies), and sniffs the generated syntax errors (via a window.onerror handler) for juicy morsels of its contents. To counter this attack, HTML5 specifies that script errors should be sanitized ("muted") when the script is not same-origin with the global for which it is loaded. Callers should set this flag for cross-origin scripts, and it will be propagated appropriately to child scripts and passed back in JSErrorReports.
JSErrorReport - Mozilla | MDN