Cannot update WordPress plugin in Plesk: ERROR: escapeshellarg(): Input string contains NULL bytes

Symptoms

• Cannot update WordPress plugin for Plesk domain:

  PLESK_ERROR: Task is not responding: id=101, pid=10110, type=ext-wp-toolkit-taskmanage

• The same above error appears on checking updates for WordPress instance in Plesk

• Error in/var/log/plesk/panel.log:

  ERR [1] ERROR: escapeshellarg(): Input string contains NULL bytes (functions.php:1209)
   DEBUG [util_exec] [] Starting: /usr/local/psa/admin/bin/php /usr/local/psa/admin/plib/scripts/task-async-executor.php -task-id 101, stdin: 
   DEBUG [util_exec] [] Finished in 0.00736s, Error code: TRUE, stdout: , stderr: 
   INFO [panel] The selected plugin will be updated on the selected WordPress installations. Note that this might take a few minutes. 
   ERR [panel] Task is not responding: id=101, pid=10110, type=ext-wp-toolkit-taskmanage

• In Plesk Onyx 17.8, it is not possible to update WordPress admin password at Domains > example.com > WordPress > Setup.

• Refreshing WordPress instance in Domains > example.com > WordPress > Refresh fails:

  Request to backend API failed with error: Request failed with status code 500

Cause

Inconsistency in the WordPress Toolkit database.

Resolution

1. Connect to the server via SSH

2. Obtain the list of IDs of domains affected by the issue:

   # plesk db “select id from domains where name=’example.com'”

3. Create WordPress Toolkit database backup:

   # cp /usr/local/psa/var/modules/wp-toolkit/wp-toolkit.sqlite3{,.orig}

4. Login to WordPress Toolkit database:

   # sqlite3 /usr/local/psa/var/modules/wp-toolkit/wp-toolkit.sqlite3

5. Obtain IDs of the WordPress instance:

   MYSQL_LIN: sqlite> .headers on
   sqlite> select id from Instances where domainId in (<IDs from step 2>);

6. Remove all rows with the IDs which is related to the instance:

   MYSQL_LIN: sqlite> delete from InstancesDomains where instanceId in (<IDs from step 5>);
   sqlite> delete from Instances where id in (<IDs from step 5>);
   sqlite> delete from InstanceProperties where instanceId in (<IDs from step 5>);

   Note: ID of the instance can be found on the URL of the instance page: Domains > example.com > WordPress > name_of_WordPress_instance.

7. Log in to Plesk and press Scan button in Domains > example.com > WordPress to register the instance in WordPress Toolkit:

8. Renew WordPress admin password