Complex Codebases: Complex codebases make it really hard to implement security consistently. This complexity makes vulnerabilities hard to detect and remediate to. Each new feature may add a set of vulnerabilities
Insufficient Security Practices: Companies may prioritize speed and deadlines leading to no code reviews, missing secure coding practices or no security testing.
Limited External Scrutiny: Limited external code reviews may lead to first-party reviews ignoring vulns or thinking the code is perfect