Laravel 5.6.30 is a security release of Laravel and is recommended as an immediate upgrade for all users. Laravel 5.6.30 also contains a breaking change to cookie encryption and serialization logic. Refer to laravel advisory for more details and read the notes carefully when upgrading your application.

References

• https://github.com/FriendsOfPHP/security-advisories/blob/master/laravel/framework/2018-08-08-1.yaml
• https://laravel.com/docs/5.6/upgrade#upgrade-5.6.30