A WordPress anti-spam plugin with over 60,000 installations covered a PHP Object injection vulnerability that developed from incorrect sanitization of inputs, subsequently allowing 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 function 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 obstruct.
It is a needed practice for any WordPress plugin or kind that accepts a user input to just enable particular inputs, like text, images, e-mail addresses, whatever input is anticipated.
Unexpected inputs must be strained. That filtering procedure that stays out unwanted inputs is called sanitization.
For instance, a contact type must have a function that examines 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 Object injection vulnerability.
The description of the vulnerability released on the WPScan website explains the problem as:
“The plugin passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are utilized as 2nd challenge, which might result in PHP Things injection if a plugin installed on the blog has an ideal gadget chain …”
The category of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Task (OWASP) describes the possible effect of these sort of vulnerabilities as severe, which may or might not be the case specific to this vulnerability.
The description at OWASP:
“The effect of deserialization flaws can not be overemphasized. These defects can cause remote code execution attacks, one of the most serious attacks possible.The service effect depends upon the protection needs of the application and information. “However OWASP also notes that exploiting this sort of vulnerability tends to be hard:”Exploitation of deserialization is somewhat hard,
as off the shelf exploits seldom work without modifications or tweaks to the underlying exploit 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 different updates)notes the repair as an enhancement for security. Users of the Stop Spam Security plugin ought to consider upgrading to the latest
version in order to avoid a hacker from exploiting the plugin. Read the main alert at the United States Government National Vulnerability Database
: CVE-2022-4120 Detail Check out the WPScan publication of information related to this vulnerability:
Stop Spammers Security