Unable to install WordPress on Plesk domain: getRiskRank(): Return value must be of type string, null returned

Symptoms

• Installing a WordPress instance on an existing or newly added domain fails with the following error:

  PLESK_ERROR: WordPress installed with errors:
  PleskExt\WpToolkit\Db\Row\Vulnerability::getRiskRank(): Return value must be of type string, null returned

• WP Toolkit has been recently updated

• This error shows in /var/log/plesk/panel.log related to the recent WP Toolkit update:

  CONFIG_TEXT: [2024-06-12 10:24:00.385] 1146307:666976f2884a8 ERR [extension/wp-toolkit] The execution of post-install.php has failed with the following message:
  PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 20480 bytes) in /opt/psa/admin/plib/modules/wp-toolkit/library/Helper/Util.php on line 174

Cause

WordPress Tookit bugs EXTWPTOOLK-11883 and EXTWPTOOLK-11884.

Resolution

Until the bug is fixed, apply the following workaround:

1. Increase the Plesk memory limit as per the following article: Operations in Plesk fail: Allowed memory size of X bytes exhausted (tried to allocate Y bytes)

2. Connect to the server via SSH and run the WP Toolkit maintenance script, which would update the vulnerabilities database as well, by executing the following command:

# plesk bin extension -e wp-toolkit maintenance.php