Input validation vulnerability in Laposta Signup Embed 1.1.1

The Laposta Signup Embed plugin for WordPress, which is used up to version 1.1.0, is vulnerable to something called Cross-Site Request Forgery. This means that it is possible for an attacker to send a malicious request to the plugin, without needing to authenticate themselves, by tricking an administrator into clicking on a link. This malicious request could then be used to clear the plugin’s cache. To prevent this security vulnerability, the plugin needs to validate all requests using something called a nonce.