FreePBX is a popular PBX system built around the open source VoIP system Asterisk. To manage Asterisk more easily, it provides a capable web-based admin interface. Sadly, like so many web applications, it has had its share of vulnerabilities in the past. Most recently, a SQL injection vulnerability was found that allows attackers to modify the database. For a PBX, there are a number of obvious attacks. For example, they are often abused for free phone calls, to impersonate the companies running the PBX, or to hide the true origin of phone calls. Manipulating the FreePBX database would certainly facilitate these types of attacks. However, I noticed some slightly more interesting attacks recently attempting to achieve complete code execution. A typical request looks like: GET…