The Extra Checkout Options (addon for Extra Product Options & Add-Ons for WooCommerce) plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.3.2. This is due to missing authorization and nonce validation in the eco_save_settings() function, which allows low-privileged authenticated users to modify the tc_eco_custom_file_types upload allowlist setting, combined with insufficient authorization on the wc_eco_upload_file AJAX action. This makes it possible for authenticated attackers, with Subscriber-level access and above, to allow PHP uploads, upload a PHP file using the frontend upload nonce exposed on cart and checkout pages, and achieve remote code execution. NOTE: This vulnerability was partially fixed in version 2.3.2.
Weakness
The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- For example, limiting filenames to alphanumeric characters can help to restrict the introduction of unintended file extensions.
- Run the code in a “jail” or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
- OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.