Pro PHP Security: From Application Security Principles to the Implementation of XSS Defenses, Second Edition

Testing for Remote Execution Vulnerabilities

Of all the vulnerabilities you can introduce into your PHP code, those that allow remote execution are probably the most serious. Security experts often make the assumption that if an attacker has free rein to execute any code he wants, even as an unprivileged user like nobody, he can find other weaknesses in the system and turn himself into the root user. That would permit him to take over the server. Whether this assumption is true for your server depends on how well you, and the thousands of other programmers who wrote the code you run, did at preventing such behavior: how many layers are there to your security onion? At any rate, the assumption has certainly proven true for many servers that have ...