PHP error

I have been told by my newsletter plugin that I need to upgrade from PHP version 7.4 since it is no longer supported.

I tried to change to PHP 8.2 but the system told me this:

Fatal error: Uncaught Error: Call to undefined function security\wordpress\vulnerabilities\openssl_decrypt() in /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities/class-rsssl-file-storage.php:113 Stack trace: #0 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities/class-rsssl-file-storage.php(52): security\wordpress\vulnerabilities\Rsssl_File_Storage->Decode64WithHash(‘RrPq9O6FU7i0PfU…’) #1 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities/class-rsssl-file-storage.php(40): security\wordpress\vulnerabilities\Rsssl_File_Storage->get(‘/home/www/vang….’) #2 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities.php(1048): security\wordpress\vulnerabilities\Rsssl_File_Storage::GetFile(‘components.json’) #3 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities.php(504): rsssl_vulnerabilities->get_components() #4 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities.php(296): rsssl_vulnerabilities->cache_installed_plugins() #5 /home/www/vang.nu/wp-includes/class-wp-hook.php(324): rsssl_vulnerabilities->show_help_notices(Array) #6 /home/www/vang.nu/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array) #7 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/class-admin.php(2400): apply_filters(‘rsssl_notices’, Array) #8 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/class-admin.php(2615): rsssl_admin->get_notices_list() #9 /home/www/vang.nu/wp-content/plugins/really-simple-ssl/settings/settings.php(174): rsssl_admin->count_plusones() #10 /home/www/vang.nu/wp-includes/class-wp-hook.php(324): rsssl_add_option_menu(”) #11 /home/www/vang.nu/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array) #12 /home/www/vang.nu/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #13 /home/www/vang.nu/wp-admin/includes/menu.php(161): do_action(‘admin_menu’, ”) #14 /home/www/vang.nu/wp-admin/menu.php(417): require_once(‘/home/www/vang….’) #15 /home/www/vang.nu/wp-admin/admin.php(158): require(‘/home/www/vang….’) #16 /home/www/vang.nu/wp-admin/index.php(10): require_once(‘/home/www/vang….’) #17 {main} thrown in /home/www/vang.nu/wp-content/plugins/really-simple-ssl/security/wordpress/vulnerabilities/class-rsssl-file-storage.php on line 113

at PHP 8.0 everything is OK although I find it a little problematic