[wp-trac] [WordPress Trac] #64347: Fatal error when `wxr_cdata()` is called with non-string value

[WordPress Trac]

#64347: Fatal error when `wxr_cdata()` is called with non-string value
--------------------------+--------------------
 Reporter:  desrosj       |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  6.9.1
Component:  Export        |    Version:  6.9
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+--------------------
 From [https://wordpress.org/support/topic/export-this-site-is-unreachable-
 err_invalid_response/ this issue] on the wp.org Support forums:

 > Hi
 >
 > During export, a page opens with this message: “This site is
 unreachable. Website at https://kamerydrogowe.wlkp.net.pl/wp-
 admin/export.php?.. may be temporarily unavailable or may have been
 permanently moved to a new internet address. ERR_INVALID_RESPONSE”
 >
 > WordPress, themes, plugins – updated. Theme enabled on Twenty tweny –
 still a problem. Plugin cache cleared, web browser cache and cookies
 cleared – still the problem. All plugins disabled – export downloads, but
 only 1.1 Mb instead of about 16 Mb.
 >
 > I also got the message: “The old WordPress core file was not removed
 during the update: wp-includes/SimplePie/src/Core.php”

 The following log output was followed in a follow up response:

 {{{
 [03-Dec-2025 20:47:17 UTC] PHP Warning:  Cannot modify header information
 - headers already sent by (output started at /wp-config.php:103) in /wp-
 includes/functions.php on line 7182
 [03-Dec-2025 20:47:17 UTC] PHP Warning:  Cannot modify header information
 - headers already sent by (output started at /wp-config.php:103) in /wp-
 admin/includes/export.php on line 96
 [03-Dec-2025 20:47:17 UTC] PHP Warning:  Cannot modify header information
 - headers already sent by (output started at /wp-config.php:103) in /wp-
 admin/includes/export.php on line 97
 [03-Dec-2025 20:47:17 UTC] PHP Warning:  Cannot modify header information
 - headers already sent by (output started at /wp-config.php:103) in /wp-
 admin/includes/export.php on line 98
 [03-Dec-2025 20:47:17 UTC] PHP Fatal error:  Uncaught TypeError:
 wp_is_valid_utf8(): Argument #1 ($bytes) must be of type string, null
 given, called in /wp-admin/includes/export.php on line 246 and defined in
 /wp-includes/utf8.php:39
 Stack trace:
 #0
 /wp-admin/includes/export.php(246): wp_is_valid_utf8(NULL)
 #1
 /wp-admin/includes/export.php(682): wxr_cdata(NULL)
 #2
 /wp-admin/export.php(123): export_wp(Array)
 #3 {main}
   thrown in
 /wp-includes/utf8.php on line 39
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/64347>
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