A WordPress anti-spam plugin with over 60,000 installations covered a PHP Object injection vulnerability that occurred from improper sanitization of inputs, subsequently enabling base64 encoded user input.
Unauthenticated PHP Object Injection
A vulnerability was found in the popular Stop Spammers Security|Block Spam Users, Remarks, Forms WordPress plugin.
The purpose of the plugin is to stop spam in comments, types, and sign-up registrations. It can stop spam bots and has the ability for users to input IP addresses to obstruct.
It is a required practice for any WordPress plugin or type that accepts a user input to just enable particular inputs, like text, images, e-mail addresses, whatever input is expected.
Unforeseen inputs need to be removed. That filtering procedure that stays out unwanted inputs is called sanitization.
For example, a contact form need to have a function that inspects what is sent and block (sterilize) anything that is not text.
The vulnerability discovered in the anti-spam plugin allowed encoded input (base64 encoded) which can then trigger a kind of vulnerability called a PHP Object injection vulnerability.
The description of the vulnerability published on the WPScan website explains the concern as:
“The plugin passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are utilized as second obstacle, which might result in PHP Things injection if a plugin set up on the blog site has an ideal gizmo chain …”
The classification of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Task (OWASP) describes the possible effect of these kinds of vulnerabilities as serious, which may or might not be the case specific to this vulnerability.
The description at OWASP:
“The impact of deserialization flaws can not be overemphasized. These flaws can cause remote code execution attacks, among the most severe attacks possible.The service impact depends on the protection requirements of the application and data. “But OWASP also notes that exploiting this sort of vulnerability tends to be difficult:”Exploitation of deserialization is rather tough,
as off the rack exploits hardly ever work without changes or tweaks to the hidden make use of code.”The vulnerability in the Stop Spammers Security WordPress
plugin was fixed in variation 2022.6 The main Stop Spammers Security changelog (a description with dates of numerous updates)notes the fix as an improvement for security. Users of the Stop Spam Security plugin must think about upgrading to the latest
version in order to prevent a hacker from exploiting the plugin. Check out the official notice at the United States Federal Government National Vulnerability Database
: CVE-2022-4120 Detail Read the WPScan publication of details connected to this vulnerability:
Stop Spammers Security