A WordPress anti-spam plugin with over 60,000 installations patched a PHP Object injection vulnerability that arose 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, Kinds 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 capability 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 just enable particular inputs, like text, images, e-mail addresses, whatever input is expected.
Unforeseen inputs need to be filtered out. That filtering procedure that stays out undesirable inputs is called sanitization.
For example, a contact kind must have a function that checks what is sent and block (sanitize) anything that is not text.
The vulnerability found in the anti-spam plugin permitted encoded input (base64 encoded) which can then trigger a kind of vulnerability called a PHP Item injection vulnerability.
The description of the vulnerability released on the WPScan site describes the problem as:
“The plugin passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are utilized as 2nd difficulty, which might result in PHP Item injection if a plugin installed on the blog site has an appropriate gadget chain …”
The category of the vulnerability is Insecure Deserialization.
The non-profit Open Web Application Security Task (OWASP) explains the possible impact of these type of vulnerabilities as severe, which might or might not hold true specific to this vulnerability.
The description at OWASP:
“The impact of deserialization defects can not be overstated. These flaws can cause remote code execution attacks, among the most serious attacks possible.The organization impact depends on the protection needs of the application and information. “But OWASP likewise keeps in mind that exploiting this sort of vulnerability tends to be hard:”Exploitation of deserialization is somewhat difficult,
as off the shelf makes use of rarely work without changes or tweaks to the underlying make use of code.”The vulnerability in the Stop Spammers Security WordPress
plugin was fixed in variation 2022.6 The official 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
variation in order to avoid a hacker from making use of the plugin. Read the main notice at the United States Government National Vulnerability Database
: CVE-2022-4120 Detail Read the WPScan publication of details associated with this vulnerability:
Stop Spammers Security