A WordPress anti-spam plugin with over 60,000 setups patched a PHP Object injection vulnerability that emerged from improper sanitization of inputs, consequently permitting base64 encoded user input.
Unauthenticated PHP Object Injection
A vulnerability was discovered in the popular Stop Spammers Security|Block Spam Users, Comments, Kinds WordPress plugin.
The function of the plugin is to stop spam in comments, types, and sign-up registrations. It can stop spam bots and has the capability for users to input IP addresses to obstruct.
It is a required practice for any WordPress plugin or form that accepts a user input to just permit particular inputs, like text, images, email addresses, whatever input is expected.
Unanticipated inputs need to be removed. That filtering procedure that stays out unwanted inputs is called sanitization.
For instance, a contact kind need 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 allowed encoded input (base64 encoded) which can then set off a type of vulnerability called a PHP Item 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 difficulty, which could cause PHP Item injection if a plugin installed on the blog site has a suitable device chain …”
The category of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Job (OWASP) explains the possible impact of these sort of vulnerabilities as severe, which might or might not hold true 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 company impact depends on the protection needs of the application and data. “However OWASP also notes that exploiting this sort of vulnerability tends to be challenging:”Exploitation of deserialization is somewhat hard,
as off the rack exploits rarely work without modifications or tweaks to the hidden make use of code.”The vulnerability in the Stop Spammers Security WordPress
plugin was repaired in version 2022.6 The official Stop Spammers Security changelog (a description with dates of various updates)notes the fix as an enhancement for security. Users of the Stop Spam Security plugin should think about upgrading to the current
version in order to prevent a hacker from making use of the plugin. Check out the main notification at the United States Federal Government National Vulnerability Database
: CVE-2022-4120 Detail Read the WPScan publication of details related to this vulnerability:
Stop Spammers Security