Modern SaaS applications handle sensitive user information, and it's crucial for web applications to adhere to the highest security standards to maintain business reputation, avoid financial losses, and protect users. Customer communications are often overlooked in terms of security, but this is a critical component that must be addressed. Many modern SaaS applications rely on cloud platforms and third-party services, which means designing security controls requires considering all these components. Specialized security measures are necessary to process personally identifiable information, such as customer records, application code, and API keys. Implementing encryption, tokenization, secure data backup, continuous monitoring, automation, and external audits can help protect sensitive user data. The importance of security in modern SaaS applications cannot be overstated, as breaches can lead to massive penalties, financial losses, and damage to reputation. With the increasing number of data breaches and sophisticated attacks, it's essential to integrate up-to-date security practices into both application development and company organization.