Inserted Code in WP

Has anyone else started seeing the following code automatically inserted into the editor window in 4.5.3? I’ve seen it now on two different sites with completely different plugin sets?

/START CODE/
<span style=”border-radius: 2px; text-indent: 20px; width: auto; padding: 0px 4px 0px 0px; text-align: center; font: bold 11px/20px ‘Helvetica Neue’,Helvetica,sans-serif; color: #ffffff; background: #bd081c no-repeat scroll 3px 50% / 14px 14px; position: absolute; opacity: 0.85; z-index: 8675309; display: none; cursor: pointer; top: 44px; left: 364px;”>Save</span>

/END CODE/