I am experiencing the same issue now after this new update. I had to deactivate the plug in. I can’t even delete it to reinstall, it says it detects a fatal error.
WordPress version 5.8
Current plugin: MailOptin – Lite (version 1.2.39.1)
PHP version 7.3.12
Error Details
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An error of type E_COMPILE_ERROR was caused in line 16 of the file /var/www/wp-content/plugins/mailoptin/mailoptin.php. Error message: require(): Failed opening required ‘/var/www/wp-content/plugins/mailoptin/vendor/autoload.php’ (include_path=’.:/opt/remi/php73/root/usr/share/pear:/opt/remi/php73/root/usr/share/php:/usr/share/pear:/usr/share/php’)
