A WordPress anti-spam plugin with over 60,000 installations patched a PHP Object injection vulnerability that arose from inappropriate sanitization of inputs, consequently enabling base64 encoded user input.
Unauthenticated PHP Object Injection
A vulnerability was discovered in the popular Stop Spammers Security|Block Spam Users, Remarks, Types WordPress plugin.
The purpose of the plugin is to stop spam in comments, forms, and sign-up registrations. It can stop spam bots and has the ability for users to input IP addresses to block.
It is a needed practice for any WordPress plugin or type that accepts a user input to just permit particular inputs, like text, images, email addresses, whatever input is anticipated.
Unforeseen inputs should be filtered out. That filtering procedure that keeps out unwanted inputs is called sanitization.
For instance, a contact kind ought to have a function that inspects what is submitted and block (sanitize) anything that is not text.
The vulnerability found in the anti-spam plugin permitted encoded input (base64 encoded) which can then set off a type of vulnerability called a PHP Things injection vulnerability.
The description of the vulnerability released on the WPScan site describes the issue as:
“The plugin passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are utilized as 2nd obstacle, which might lead to PHP Object injection if a plugin set up on the blog has an appropriate gizmo chain …”
The category of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Job (OWASP) describes the prospective impact of these sort of vulnerabilities as major, which may or might not hold true specific to this vulnerability.
The description at OWASP:
“The impact of deserialization flaws can not be overemphasized. These flaws can lead to remote code execution attacks, among the most severe attacks possible.The organization effect depends on the protection requirements of the application and data. “But OWASP also notes that exploiting this kind of vulnerability tends to be tough:”Exploitation of deserialization is rather hard,
as off the rack exploits rarely work without modifications or tweaks to the underlying exploit code.”The vulnerability in the Stop Spammers Security WordPress
plugin was repaired in variation 2022.6 The main Stop Spammers Security changelog (a description with dates of different updates)notes the fix as an improvement for security. Users of the Stop Spam Security plugin need to consider updating to the latest
version in order to prevent a hacker from making use of the plugin. Read the official notification at the United States Government National Vulnerability Database
: CVE-2022-4120 Information Check out the WPScan publication of details associated with this vulnerability:
Stop Spammers Security