[wp-trac] [WordPress Trac] #39338: class-wp-hook.php - apply_filters() infinite loop

[WordPress Trac]

#39338: class-wp-hook.php - apply_filters() infinite loop
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 Reporter:  frettled           |       Owner:
     Type:  defect (bug)       |      Status:  new
 Priority:  normal             |   Milestone:  Awaiting Review
Component:  Plugins            |     Version:  4.7
 Severity:  normal             |  Resolution:
 Keywords:  reporter-feedback  |     Focuses:
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Comment (by frettled):

 Replying to [comment:2 dd32]:
 > Hi @frettled and welcome to Trac.
 >
 > Are you able to offer any extra specific details about how this scenario
 was triggered? For example, the hook name which was executing and anything
 which was hooked onto it, or all plugins in use on the site?

 This specific bug had referer: hxxp://.../wp-includes/admin.php?page
 =mediafromftp-settings which leads me to guess that there was something
 about the plugin mediafromftp that initialized the problem.

 > Protecting against this is something we should do, however in order to
 do that effectively, we need to determine how and why it happens to test
 it.
 > I've tried a few random combinations and I can't get it in a situation
 where `$this->iterations[ $nesting_level ]` is unset.

 I have a total of three error messages repeating infinitely, until the
 process is killed by a monitoring script:

 1) line 287: current() expects parameter 1 to be array, null given in
 .../wp-includes/class-wp-hook.php on line 287

 2) line 289: Invalid argument supplied for foreach() in .../wp-includes
 /class-wp-hook.php on line 289

 3) line 303: next() expects parameter 1 to be array, null given in .../wp-
 includes/class-wp-hook.php on line 303

 Digging into the logs for non-matching errors from the same website, I see
 another error which may be related:

 array_keys() expects parameter 1 to be array, integer given in ../wp-
 includes/class-wp-hook.php on line 283

 On this line, it's extracting from $this->callbacks.

 So perhaps that's a better place for a check.

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Ticket URL: <https://core.trac.wordpress.org/ticket/39338#comment:3>
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