Software development does not always follow a well-structured process. Some companies tend to give developers more flexibility than others, which often results in critical vulnerabilities and high rework activities. Therefore, independent whether your projects follow agile or waterfall development principles, you shall apply some basic secure software development principles to avoid security loopholes.
Two of three security breaches account to vulnerable applications. Cyber criminals use your weak business applications to get access to confidential data without beeing detected.