When it comes to insecure code in WordPress plugins, beyond insecure code written by the developers, we often find that the developers have included code created by others without reviewing its security first (that even has been the case with popular security plugins). Recently multiple security issues were fixed in the plugin Sliced Invoices, while looking into that we found that plugin Tradies has copied a significant amount of code from that plugin and still contains those vulnerabilities, so significant that if you try to activate Tradies with Sliced Invoices already activated (or vice versa) it won’t work because a class name is reused. While that is permitted by the GPL, there isn’t a copyright statement indicating the source of the code (which isn’t the first time we have seen that done with copied code).
As an example of the insecure code copied, let’s take a look at the code to handle exporting the plugin’s quotes and invoices. [Read more]