When I talk to people about application security, the most recognized topics is the OWASP Top 10. If you haven’t heard of the top 10, or need a refresher, you can get the full list at:
The OWASP Top 10 is on a three year update cycle. We had the list in 2010, 2013 and now the latest is 2017. You may be wondering why it is 2017 rather than 2016. I think that is a question a lot of people had. In any case, the list made it out to final release after the initial draft was rejected. Now that it is here, we can analyze it and see how it affects us and our organizations.
What I think sticks out more to me this update over previous updates is the removal of some pretty common flaws based on my experience. In the past we have seen flaws move up or down on the risk level, or get combined, but not as much removed. In 2017, we saw two items get removed:
- Cross-site Request Forgery
- Unvalidated Redirects and Forwards
I find these items interesting because I see them on most of the assessments I do. Let’s take a quick look at them.
Cross-site Request Forgery
CSRF can be a pretty serious flaw based on its context. It is the ability to force the victim’s browser to make requests to another site they are authenticated too without their knowledge. An example of a higher-risk context is the ability to change the victim’s email address on their profile. If the system doesn’t have two factor authentication or other safe guards, changing the email address can lead to the ability to request a password reset. In many situations, this can lead to easily taking over the victim’s account.
This is just one example of how CSRF can be used. The good news is that many newer frameworks provide some level of CSRF protection built-in. So in many applications it is not as prevalent. However, based on my experience, not everyone is using the latest frameworks. Due to this, I still find this on a lot of the assessments I do.
Unvalidated Redirects and Forwards
Unvalidated Redirects is often viewed as a low risk issue. In many cases, it may represent a low risk. There are some situations that make unvalidated redirects fairly dangerous. A good example is the redirect often performed by login forms. A common feature of many applications is to redirect the user to a specific resource after logging in. To do this, a parameter in the URL specifies the path to be sent to. If the application allows redirecting to external sites, it is simple to set up a malicious site with the same look and feel as the expected site. If the victim uses your link with the reference to your malicious site they may be presented with your fake login page after successfully logging into the real site. The victim may believe they have mistyped their password and just login again without checking the URL, leading to account takeover.
We also saw to access control findings get merged into one. This change makes a lot of sense when you look at each item. They are both regarding access control issues.
With the removal and merging, the list has brought on three new vulnerabilities:
- XML External Entities (XXE)
- Insecure Deserialization
- Insufficient Logging and Monitoring
XML External Entities (XXE)
XML External Entities is a vulnerability that takes advantage of how XML Parsers interpret the supplied XML. In this case, it is possible to reference other resources outside of the XML document. A common scenario is the ability to read other files on the web server, such as the /etc/passwd file. This vulnerability also may allow a denial of service attack to occur due to embedding specific entities. This vulnerability obviously relies on the application parsing XML data. If your application is parsing XML, it is recommended to make sure the parser is ignoring or blocking DTDs. If your parser doesn’t have that option, or you need to allow some DTDs, make sure your input validation is limiting those to only acceptable ones.
Insecure Deserialization occurs when you are deserializing data that has not been properly sanitized. This occurs because we assume that the data serialized has not been modified. When the data is modified, it could be executed during the deserialization process to perform commands. To help prevent this, make sure you are enforcing strict data checks on the objects that have been serialized. I do not see this very often in many of the assessments I do. Just depends on the application as many do not use much serialization.
Insufficient Logging and Monitoring
When I talk to people and ask them about logging, the first response, or usually the only response, is related to troubleshooting. There is no doubt that troubleshooting is critical for any application. If the application is not running as expected, users may leave, transactions may get lost, or a myriad of other issues may occur. Logging is for much more than just troubleshooting. Proper logging of security related events can help identify an attack while it is occurring as well as help identify what happened after the fact. It can be very difficult to identify what data was accessed or how if there are no logs indicating such information. It is good that we are seeing more attention called to this practice, although it can be a complex one to implement and verify. Don’t forget that once you start logging security events, they must be monitored to take action.
Changes to the OWASP Top 10 isn’t something new. We know it will happen and it may require some adjustment to what we are doing internally. While we do see items drop or get added, it just highlights that the top 10 is a mere starting point of security. Every organization should have their list of top 10 risks. Don’t limit yourself to these short lists. They are to help identify the highest risks and implement them in a feasible way. Application security doesn’t happen overnight. There has to be a starting point and then a path to mature.
Listen to the podcast on this topic. http://podcast.developsec.com/developsec-podcast-91-owasp-top-10-2017-thoughts