execCommand[0] has a &quot;paste&quot; option, which pastes the content of the clipboard at the current insertion point.  This allows for &quot;reading&quot; of the clipboard.<p>This article doesn&#x27;t mention &quot;paste&quot; specifically, but the footnote[1] in the &quot;paste&quot; section says:<p><i>&quot;[1] Before Firefox 41, clipboard capability needed to be enabled in the user.js preference file. See A brief guide to Mozilla preferences for more information. In Firefox 41 and later, clipboard capability are enabled by default in any event handler that is able to pop-up a window (semi-trusted scripts).&quot;</i><p>This footnote is not attached to any other command, and thus &quot;paste&quot; is singled out.  This could just be a documentation error, or maybe they didn&#x27;t want to highlight that paste was also being enabled.  I don&#x27;t have a FF v41 in order to test what the actual behavior is.<p>[0] - <a href="https:&#x2F;&#x2F;developer.mozilla.org&#x2F;en-US&#x2F;docs&#x2F;Web&#x2F;API&#x2F;Document&#x2F;execCommand" rel="nofollow">https:&#x2F;&#x2F;developer.mozilla.org&#x2F;en-US&#x2F;docs&#x2F;Web&#x2F;API&#x2F;Document&#x2F;ex...</a>