This document discusses common security vulnerabilities in plugins and how to prevent them. It covers cross-site scripting (XSS) vulnerabilities, which can allow attackers to run JavaScript in a victim's browser. It also discusses cross-site request forgery (XSRF) vulnerabilities, which trick a victim into performing unwanted actions. The document provides guidance on using HTML encoding, generating secure random numbers, restricting file system access, and other techniques to prevent these vulnerabilities. It focuses on securing plugins used in Atlassian products like JIRA, Confluence and Bamboo.