Bug in mu-plugins/kinsta-mu-plugins on Astra theme update

Feedback
1

I saw this error bubble up today:

2026.01.06. 12:56:14
[error] 86494#86494: *1800216 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in /www/knepp_839/public/wp-content/mu-plugins/kinsta-mu-plugins/app/Cache/Autopurge/WPThemeController.php:25
2026.01.06. 12:56:14
Stack trace:
2026.01.06. 12:56:14
#0 /www/knepp_839/public/wp-content/mu-plugins/kinsta-mu-plugins/app/Cache/Autopurge/WPThemeController.php(25): in_array('knepp', NULL, true)
2026.01.06. 12:56:14
#1 /www/knepp_839/public/wp-includes/class-wp-hook.php(341): Kinsta\KMP\Cache\Autopurge\WPThemeController->{closure:Kinsta\KMP\Cache\Autopurge\WPThemeController::hook():17}(Object(Theme_Upgrader), Array)
2026.01.06. 12:56:14
#2 /www/knepp_839/public/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array)
2026.01.06. 12:56:14
#3 /www/knepp_839/public/wp-includes/plugin.php(522): WP_Hook->do_action(Array)
2026.01.06. 12:56:14
#4 /www/knepp_839/public/wp-admin/includes/class-wp-upgrader.php(987): do_action('upgrader_proces...', Object(Theme_Upgrader), Array)
2026.01.06. 12:56:14
#5 /www/knepp_839/public/wp-admin/includes/class-theme-upgrader.php(324): WP_Upgrader->run(Array)

I have Astra as the theme and I upgrade it via the link it injects where, after you update the plugin, it puts a notice saying “update theme if not already done so”.

The link that it injects into that goes directly to the install / update process. At the end it showed a fatal error, underneath the normal “installing…” type messages.

The site didn’t go down, so its a minor thing but obviously that is sending some data in an unexpected way.

Probably a pretty simple fix if you throw it at an AI, so I thought I would share it here.

2

Thanks for the report @rtpHarry . Can you confirm the current version of the Kinsta MU plugin the site is using? Also, is the site using a WP Pusher plugin? Thanks!