More than half of all software applications failed to meet an acceptable level of security, according to a study based on real-world code audits by application security firm Veracode.

Around 57 per cent of applications failed to pass muster when first submitted to Veracode’s cloud-based testing service. A similar 56 per cent of finance-related applications failed first testing by Veracode’s security audit. The quality of the code used in many business-critical banking and insurance operations was simply not up to snuff.

Cross-site scripting was the most common vulnerability, accounting for 51 per cent of vulnerabilities uncovered during the testing process. Web applications developed in .NET were particularly susceptible to this class of flaw.

Cross-site scripting holes were to blame for the worms that spread on Twitter on Tuesday. In other environments they can be used in either phishing or drive-by download attacks.

Veracode said eight out of 10 web applications would fail a PCI audit, because they failed against one or other of the top 10 application security risks as defined by OWASP.

Third-party code makes up nearly 30 per cent of all applications submitted to Veracode for review, and third-party components make up a substantial proportion of internal developed applications. Applications developed by third parties had lower security quality than those developed in-house, failing to reach acceptable security standards 81 per cent of the time, according to Veracode.

One positive finding in the otherwise gloomy survey is that developers are repairing security vulnerabilities more quickly. Development teams using Veracode were able to fix problems in 16 days, on average, compared to the 30 days recorded in previous edition of the same study.

Matt Peachey, Veracode’s VP EMEA, said: "Developers continue to focus on functionality, quality, and speed of release. Security slows down The process and often gets overlooked.

"Many of the problems, such as cross-site scripting, are down to sloppy coding. This class of flaw is well known and documented as well as easy to fix but continue to very common."

Veracode's study is based on more than 2,900 applications that were put through their paces over the last 18 months through the Veracode SecurityReview cloud-based Platform. Billions of lines of scanned code from internally developed, commercial, open source and outsourced software running in large enterprises was parsed for problems using this process.

An analysis of this feature was published on Wednesday as part of Veracode's second annual State of Software Security Report. ®