OWASP Top 10 Security Vulnerabilities
The OWASP Top 10 list for the year 2013 doesn't differ much from lists published for previous years, except for changes in ranking. The listed security threats are probably the most severe threats and application developers have to be aware of and protect against these threats.
General descriptions for the OWAP Top 10 list of security risks are documented at:
Parent topic: Secure Development Guide