A WordPress anti-spam plugin with over 60,000 installations covered a PHP Object injection vulnerability that developed from improper sanitization of inputs, consequently permitting base64 encoded user input.
Unauthenticated PHP Item Injection
A vulnerability was discovered in the popular Stop Spammers Security|Block Spam Users, Comments, Forms WordPress plugin.
The purpose of the plugin is to stop spam in remarks, kinds, 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 form that accepts a user input to only allow particular inputs, like text, images, e-mail addresses, whatever input is anticipated.
Unexpected inputs should be strained. That filtering process that stays out undesirable inputs is called sanitization.
For example, a contact type must have a function that inspects what is submitted and block (sanitize) anything that is not text.
The vulnerability discovered in the anti-spam plugin enabled encoded input (base64 encoded) which can then activate a type of vulnerability called a PHP Things injection vulnerability.
The description of the vulnerability released on the WPScan site explains the issue as:
“The plugin passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are utilized as 2nd challenge, which could lead to PHP Item injection if a plugin set up on the blog site has an appropriate gadget chain …”
The classification of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Project (OWASP) explains the potential effect of these type of vulnerabilities as severe, which may or might not be the case specific to this vulnerability.
The description at OWASP:
“The effect of deserialization defects can not be overemphasized. These defects can cause remote code execution attacks, one of the most severe attacks possible.The business effect depends upon the defense needs of the application and data. “However OWASP likewise notes that exploiting this sort of vulnerability tends to be difficult:”Exploitation of deserialization is somewhat tough,
as off the shelf exploits hardly ever work without changes or tweaks to the underlying make use of code.”The vulnerability in the Stop Spammers Security WordPress
plugin was fixed in version 2022.6 The main Stop Spammers Security changelog (a description with dates of different updates)keeps in mind the repair as an enhancement for security. Users of the Stop Spam Security plugin should think about upgrading to the latest
variation in order to avoid a hacker from exploiting the plugin. Read the main notification at the United States Government National Vulnerability Database
: CVE-2022-4120 Information Read the WPScan publication of information related to this vulnerability:
Stop Spammers Security