[wp-trac] [WordPress Trac] #38294: Visual editor hangs in Chrome and Firefox when a sequence of no-break spaces follows a paragraph

[WordPress Trac]

#38294: Visual editor hangs in Chrome and Firefox when a sequence of no-break
spaces follows a paragraph
---------------------------+-----------------------------
 Reporter:  greatislander  |      Owner:
     Type:  defect (bug)   |     Status:  new
 Priority:  normal         |  Milestone:  Awaiting Review
Component:  TinyMCE        |    Version:  4.6.1
 Severity:  normal         |   Keywords:
  Focuses:                 |
---------------------------+-----------------------------
 '''Problem'''

 A line of text wrapped in `<p>` tags followed immediately by ~30 no-break
 space characters (U+00A0) and additional text causes the visual editor to
 become unresponsive in Chrome and Firefox on macOS Sierra.

 '''Steps to Reproduce'''

 1. Insert the following content into the text editor of a post or page
 (note that the spaces preceding the asterisk are no-break spaces):

 {{{
 <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam
 nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed
 diam voluptua.</p>
                                *
 }}}

 2. Save the post or page.

 3. Switch to the visual editor.

 '''Expected Behaviour'''

 A WYSIWYG version of the content is displayed.

 '''Actual Behaviour'''

 The user receives the error message "The following page has become
 unresponsive. You can wait for it to become responsive or kill it."
 (Chrome) or "A script on this page may be busy, or it may have stopped
 responding. You can stop the script now, open the script in the debugger,
 or let the script continue." (Firefox). In some cases, letting the script
 continue will eventually load the visual editor properly.

 '''Versions'''

 * WordPress v4.6.1
 * Twenty Sixteen v1.3
 * PHP 7.0 + MariaDB
 * macOS Sierra 10.12
 * Google Chrome 53.0.2785.143 (64-bit)
 * Firefox 45.0.2

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Ticket URL: <https://core.trac.wordpress.org/ticket/38294>
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