Securing Legacy SaaS Accounting Software: A Comprehensive Review and Remediation

Client Overview
A rapidly growing company offering accounting software as a SaaS expanded its platform by adding features such as custom reports, cloud integrations, and API support. The platform, however, was built on legacy PHP code, and the traditional development approach, along with complex customizations, led to numerous security issues that were difficult to prioritize and resolve.

Challenges

  • The platform was built on outdated PHP code, which made it prone to security vulnerabilities.
  • The rapid addition of features introduced multiple layers of complexity, increasing the risk of security flaws.
  • The existing development process lacked modern security practices, resulting in a backlog of security issues that were hard to address and prioritize.
  • The company struggled to identify and fix security vulnerabilities efficiently, especially those related to input validation, output encoding, injections, and file uploads.


Blueinfy's Approach
To address these challenges, Blueinfy proposed a combined manual black-box testing and code review approach using their in-house tools. This approach was tailored to the specific needs of the legacy PHP environment and focused on identifying and resolving critical security issues.

1. Comprehensive Product Understanding
Blueinfy’s team took the time to thoroughly understand the product, its architecture, and the existing security measures in place. This deep understanding allowed them to tailor their approach to the unique challenges of the platform.
2. Manual Black-Box Testing
The team conducted manual black-box penetration testing to simulate real-world attack scenarios. This testing was aimed at uncovering security vulnerabilities without prior knowledge of the internal code, focusing on areas like input validation, output encoding, and file uploads.
3. In-Depth Code Review
Parallel to the black-box testing, Blueinfy’s code review team analyzed the PHP codebase to trace the root causes of the issues identified. The review focused on common security concerns such as SQL injection, cross-site scripting (XSS), and improper data handling.
4. Correlation of Findings
The code review team correlated the results from the black-box tests with the underlying code issues, identifying common root causes and providing targeted recommendations for remediation.

Results
The combined approach led to the identification of several high-severity vulnerabilities that were previously overlooked or not fully understood. Blueinfy delivered a detailed report that highlighted these findings and provided clear, actionable recommendations for fixing them.

  • The report prioritized the most critical security issues, enabling the client to focus on what mattered most.
  • Blueinfy’s recommendations were tailored to the legacy PHP environment, ensuring that the fixes were both effective and feasible to implement.
  • The client implemented the suggested fixes, resulting in a significantly more secure application.

Conclusion
Blueinfy’s combined manual black-box and code review approach provided the client with a clear path to securing their legacy PHP-based accounting software. By focusing on both the surface-level vulnerabilities and their underlying causes, Blueinfy helped the company address critical security issues, ensuring the platform was robust and secure for its users.

Article by Amish Shah