CSV Injection vulnerability is rare and somewhat controversial vulnerability which has been found in less than 100 WordPress plugins over the recent years. In the Patchstack bug bounty program, where security researchers can report any vulnerabilities found in any WordPress plugins in the ecosystem – we’ve made a decision to not accept CSV vulnerability reports at all.
CSV files are commonly used for data exports, but because they are plain text files, they don’t distinguish between text and formula syntax, which can lead to unexpected issues.
What Causes a CSV Injection Vulnerability?
CSV Injection occurs when user-provided values are directly inserted into an exported CSV file. When this CSV file is opened in applications like Microsoft Excel, malicious values in the CSV can execute commands if they contain specific formula syntax.
If user input begins with characters such as =, +, -, or @, spreadsheet applications may interpret this data as a formula rather than plain text. This can lead to security risks, as these formulas may execute commands on the end user’s computer, potentially exposing sensitive information or even executing harmful commands if macros are enabled.
However, there is currently no evidence of mass exploitation of CSV Injection vulnerabilities in the WordPress ecosystem. This lack of widespread attacks is likely due to the specific plugin use cases needed to enable such an attack and the complexity involved in executing it successfully.
What Can Happen If Your WordPress Website Has a CSV Injection Vulnerability?
CSV Injection vulnerabilities are typically classified as low to medium severity. For a CSV Injection exploit to be successful, the generated CSV file must be opened in an application that allows formula execution. Such an exploit also requires multiple steps, possibly involving social engineering to convince a high-privileged user to export or download the CSV file and then open it in a vulnerable application.
If exploited, a CSV Injection vulnerability could lead to serious consequences, especially if a website administrator or employee downloads and opens a maliciously crafted CSV file. These consequences may include:
- Unauthorized Code Execution: If the CSV contains formulas that trigger macros, harmful commands could be executed on the victim’s device, potentially leading to malware infection or theft of sensitive information.
- Data Leakage: An attack could trick the user into unknowingly sending sensitive data, such as login credentials, to an attacker via data-exfiltration formulas within the CSV.
How Can WordPress Developers Prevent CSV Injection Vulnerabilities?
Plugin developers can mitigate CSV Injection by sanitizing user input. Specific characters associated with functions should be escaped with a quote. By passing the CSV row (the array of values for one row, typically used in conjunction with fputcsv) to a sanitization function, developers can ensure that dangerous characters are properly escaped. Additionally, developers should carefully manage what data is allowed in CSV exports and restrict access to authorized users.
For web developers building WordPress sites, it’s best to use plugins only with essential functionality. If a plugin includes a CSV export feature but it’s not essential, consider disabling it or using an alternative. Keeping plugins updated and monitoring for new security vulnerabilities is also critical, enabling you to address vulnerabilities before they can be exploited.
Some additional resources:
Oliver Sild
Oliver Sild is the CEO and Co-founder of Patchstack. He is an entrepreneur and cyber security expert with a strong focus on community building. He has been organising hacking competitions (& local CTF community) in Estonia since 2016, has kickstarted a startup community in his hometown and has nearly 10 years of experience with WordPress security.
