Issue with Leaky Paywall Group Accounts Plugin

[paulness]

Wordpress version
5.9.4
MySQL Version
5.6
Leaky Paywall Group Account Plugin Version
1.4.1

File
web/app/plugins/leaky-paywall-group-accounts/functions.php

Issue
Calls made to get_users with the compare flag of 'EXISTS' for the single item of group_id are resulting in an invalid query being produced that fails with MySQL, there is likely a deep issue with the dynamic query generation in Wordpress in this file wordpress\wp-includes\class-wp-meta-query.php when using EXISTS for single values in some setups. Which results in this invalid query SELECT * FROM artnetnews.wp_usermeta WHERE meta_key = '_leaky_paywall_group_member' AND CAST(meta_value AS CHAR) EXISTS '2228566' ORDER BY CAST(meta_value AS CHAR see line 773 of web/app/plugins/leaky-paywall-group-accounts/functions.php attached

The query has a CAST followed by an EXISTS which is invalid

Recommended action
Since group_id is a single value, I recommend changing the compare flag to = from EXISTS and resolves the problem with our version of Wordpress and MySQL.

Attached files
class-wp-meta-query.zip

Image of the issue on the Group Accounts page with the stock plugin

Image of the Group Accounts page with the modification (fixed)

Other links
https://developer.wordpress.org/reference/classes/wp_meta_query/__construct/