<p>Welcome to a pre-release version of t<strong>he xEditor distribution!</strong> Our goal is to greatly improve the authoring experience of Drupal, through a <em>Drupal 7</em> distribution that can be used today, <strong>but can also</strong> be proposed as Drupal 8 core improvements for tomorrow. Read on for more info! <strong>Please take a look around!</strong> Within, you will find such nifty features as:</p>

Details:

If I select anything before <strong> tag I don't have any problem problem, but if I select anything from <strong> and or anything till the end of the content then I get this kind of error