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AppSec Experts React to the OWASP Top 10 2021

The Open Web Application Security Project (OWASP) celebrated its 20th anniversary on Friday, September 24. On the same day, it released updates to the OWASP Top 10 – for the first time since 2017. Big steps toward application security maturity

I attended OWASP Executive Director Andrew van der Stock’s warmup presentation where he spoke about the updates. He mentioned that many of the changes stem from improvements in the methodology brought in by a new OWASP co-lead, Brian Glas. Notably, this version of the OWASP Top 10 is “more data-driven than ever.”  

It sourced its data from pentesting vendors, bug bounty vendors, and organizations that contribute internal testing data. This year, the authors gathered data from the testing of over 500,000 applications. There are also two risks on the list that were sourced from a community survey of front-line application security and development experts. You can read more about the OWASP Top 10 methodology online here and below is an overview of the changes, 2017 versus 2021.

Overview of the OWASP Top 10 changes, 2017 versus 2021.

Speaking of front-line application security and development experts, I wanted to dig a little deeper into the OWASP Top 10 2021 and hear from folks who are influenced by the update. So, I reached out to a few of my NetSPI colleagues who specialize in application security and application penetration testing – Managing Director Nabil Hannan and Practice Director Antti Rantasaari – well as a bench of noteworthy AppSec experts – Diana Kelley (Security Curve), Jeff Williams (Contrast Security), and Peter Lukas (Code42) – to get their take on the most critical changes and how it will impact the security community. 

TL;DR – 5 key themes observed across the responses 

  1. A04: Insecure Design receives a warm welcome. 
  2. Broken Access Control moving to the top of the list is timely, and an indicator of a shift in AppSec strategy.
  3. Cloud adoption is driving the prevalence of Server-Side Request Forgery (SSRF).
  4. A strong focus on security within the SDLC; Approaching security challenges at the root.
  5. The list moves past specific individual vulnerabilities and focuses on categories of risk. 

What surprises or interests you most about the OWASP Top 10 2021? 

I’ll start! For me, the fall of Injection was the most surprising change. Injection has been the highest-ranked risk since 2007. The 2021 version of the Top 10 sees Injection fall to third place, even with XSS (which was A02 in 2010) getting rolled into it. While there are several factors related to this change, the efficacy of the OWASP Top 10 as an awareness-raising tool, and the growing use of secure-by-default frameworks which implement protections against many forms of injection are most prominent.  

Here’s what our expert panel found most shocking or interesting about the updated Top 10: 

Peter Lukas, Security Architect, Code42:  

The updates to the OWASP Top 10 are out, and there are some noteworthy conclusions that can be drawn from them. Most interestingly, Broken Authentication has fallen from position A02 to position A07, while Broken Access Control has surged to the very top of the list! This tells me that we’re getting better at locking the front door, and we really need to shift our focus on where users are entitled to go once inside our application environment.” 

Antti Rantasaari, Practice Director, NetSPI 

The OWASP Top 10 2021 moves a bit further from vulnerabilities and more towards design and the SDLC. The Top 10 list has been more vulnerability-focused in the past, and now we are seeing very broad categories, like Insecure Design. Broken Access Control moving to A01 makes a lot of sense – that is the most common high-severity vulnerability that we identify during our penetration testing.” 

Diana Kelley, CTO and Founding Partner, Security Curve:  

“Not exactly surprised, but it was really interesting and timely to see Broken Access Control move to the top of the list. I am a little disappointed to see Cryptographic Failures up at number two because we have a lot of great tools – many that are built into the most commonly used development frameworks – to help us implement crypto and crypto key management securely.” 

Nabil Hannan, Managing Director, NetSPI:  

The most surprising change – in a good way – is the fact that the list now includes Insecure Design. Having worked in the AppSec space for the last 15 years, from empirical data I’ve seen that the split between design flaws and security bugs is 50/50. The challenge with design flaws is that it usually requires a human to identify the vulnerability, usually through some type of secure design review or threat modeling activity that focuses on breaking the software. This indicates that organizations are going beyond just identifying security bugs and are starting to look for design-level flaws more proactively. 

Additionally, it is important to note that organizations need to maintain a living list of the most common types of vulnerabilities that they want to eliminate in their organization’s software. Usually, this needs to be a list of top 3-4 vulnerabilities to ensure there’s a proper focus on the vulnerabilities. Usually, this can be done with real data from various types of security assessments that are being performed to identify and fix vulnerabilities. These types of lists should be used to drive change, simply publishing a list won’t drive change, but using the list to fix –or if possible, eradicate – certain vulnerabilities is necessary.” 

Jeff Williams, Co-Founder and CTO, Contrast Security:  

I was most glad to see that the scope of the Top 10 has expanded to include the entire software supply chain and the entire software lifecycle. In particular, I welcome the new Insecure Design item which will encourage practices like threat modeling and security architecture. I also think it’s great that, in the wake of the SolarWinds and Kasaya breaches, the team included the Software Integrity category. This will help to ensure that the software we create is actually the software that gets delivered into production and doesn’t contain malware. 

The data science behind the OWASP Top 10 is phenomenal. Data from over 500 thousand real-world applications and APIs. I really wish they had included data about real-world attacks as this would have greatly expanded our understanding about which of these vulnerabilities are being attacked, how prevalent are the attacks, and which attacks actually reach their targeted vulnerability.” 

There are three new vulnerabilities on the list: Server-Side Request Forgery (SSRF), Software and Data Integrity Failures, and Insecure Design. Why do you think these vulnerabilities have become more prevalent? 

It is important to note that these three new categories are the result of an important change in the data gathering methodology. In previous versions of the OWASP Top 10, data contributors were asked to report statistics on defect discovery findings that mapped to 70 specific CWEs (weakness categories, as defined by MITRE’s Common Weakness Enumeration project). Data for any findings that did not map to those CWEs were not previously gathered. This resulted in a huge selection bias. How huge? For the first time, the 2021 Top 10 instead asked data contributors to submit statistics for all CWEs, resulting in responses with findings data for almost 700 CWEs! Considering this 90% increase in CWEs evaluated, it’s not surprising to see the emergence of these three new categories: SSRF, Software and Data Integrity Failures, and Insecure Design. 

More thoughts on the three new categories from our AppSec experts:  

Diana Kelley, CTO and Founding Partner, Security Curve:  

“I am absolutely thrilled that Insecure Design was added as a new category. Past Top 10s have focused on the technical implementation, which occurs after the design phase. However, a lot of mistakes are introduced through a problematic design… as you might imagine from it being reflected in this list, this happens a lot. The earlier a problem can be identified and addressed, the better. Better, more security-aware design processes should result in stronger, more resilient software.  

I’m also very happy to see Software and Data Integrity because, as described by OWASP, this is getting into the area of software supply chain assurance. As we saw with SolarWinds, even patches and updates can be an infection vector. Highlighting the importance of checking code updates before applying them is welcome and should contribute to overall software security at organizations.  

SSRF is an interesting addition. This has always been an issue to watch for, but one of the reasons it might be becoming more prevalent now is the ubiquity of application designs built around REST – service-based architecture and microservices, particularly those delivered via the cloud. As REST becomes a more prevalent mode of application design and delivery, the more we would expect misconfigured services to add to this problem. The fact that we’re seeing it on the list reflects the reality of how modern applications are built, so I’m glad to see it there.” 

Peter Lukas, Security Architect, Code42:  

“The inclusion of Insecure Design (A04:2021), Software and Data Integrity Failures (A07:2021) and Server-Side Request Forgery (A09:2021) reflect trends we’ve been observing in our own penetration testing and bug bounty programs. The prevalence of containerized services, reverse-proxies, and other cloned-from-the-repo microservices are making it easy for our developers to get code out the door while giving attackers the opportunity to inconspicuously take advantage of the trust we’ve placed in common automation and orchestration components. Today, our developers are not only tasked with securing the application but, thanks to those components, the application environment as well. I can see this added responsibility reflected in these updates for 2021.” 

Antti Rantasaari, Practice Director, NetSPI 

“Like OWASP states, the Top 10 list is intended to bring awareness to application security risks, and two of the new categories, Software and Data Integrity Failures and Insecure Design, are certainly important for secure software development. These issues may not be more prevalent than before; rather, their addition reflects OWASP’s move away from top 10 vulnerabilities to the top 10 application security categories.

SSRF is the only individually listed vulnerability while the other items on the Top 10 list are broad categories. Access to REST APIs and cloud provider metadata services via SSRF, most commonly restricted to GET requests, have increased the impact and raised the profile of the attack.”  

Jeff Williams, Co-Founder and CTO, Contrast Security:  

“SSRF is a great addition. Even though the backward-looking data science doesn’t support it, I think it’s smart to include a few forward-looking items in the list. This is a practice I started when I ran the OWASP Top 10 project many years ago. SSRF in particular is a serious problem for modern API-driven applications and is clearly where the puck is going. Both Software Integrity and Insecure Design are interesting items that dramatically expand the scope of the OWASP Top 10. I think it’s great that the team is moving past specific individual vulnerabilities and focusing on whole categories of problem, as well as expanding to covering parts of the software development lifecycle that are the root cause of problems.” 

Nabil Hannan, Managing Director, NetSPI:  

“The three new vulnerabilities in the list are indicative of how the industry is shifting its focus on security from being a check-the-box activity to proactively identifying and fixing vulnerabilities. Regarding SSRF with more and more organizations migrating to the cloud and adopting an API based design paradigm, SSRF is becoming more prevalent. Regarding Data Integrity Failures and Insecure Design, there is more focus these days on making sure software systems are being designed properly and whether the design is secure or not – which is a step in the right direction to proactively building secure software.” 

Final Thoughts on the OWASP Top 10 2021 

The 2017 OWASP Top 10 had data from 50,000 assessments of web applications. This year’s version has ten times that amount. In addition, this year the data-gathering process required contributors to differentiate between initial test data and retest data. Previous versions of the Top 10 treated initial-test and retest data identically, which is problematic for defect discovery methods that let developers quickly and inexpensively rescan their code. Such behavior can cause ballooning of defects easily discovered through certain automated methods. I’m glad to see this problem solved in this year’s methodology. 

Injection findings moving down on the list is a testament to the effectiveness of the OWASP Top 10. Collaborating to create awareness for the most common web application security risks is critical. Along those same lines, for years people have been incorporating the OWASP Top 10 into their standards, for instance, PCI. OWASP had been averse to this, considering it is a volunteer organization. However, they’ve had a change of heart and the 2021 release includes guidance on how to use it as a standard and how to begin to develop an application security program with it.  

However you choose to leverage the OWASP Top 10, it’s evident that – queue Bob Dylan – the times they are a-changin’. I applaud the OWASP authors and contributors for making the necessary updates to the list and its methodology. It’s a significant step towards improving the maturity of the world’s application security programs and practices.  

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