Following yesterday’s major security breach of the controversial imageboard 4chan, hackers have publicly revealed the sophisticated exploit method used to gain access to the site’s backend systems.

The attack, which took the platform offline for several hours, has exposed sensitive internal data including source code, moderator information, and administrative tools.

In a detailed post shared by Threat Actor, the hackers explained that contrary to initial speculation, the breach did not involve SQL injection techniques. Instead, they exploited a vulnerability in how 4chan processes uploaded files on certain boards including /g/, /pol/, /qst/, /sci/, and /lg/1.

“They neglected to verify that the uploaded file is actually a PDF file,” stated the revelation post. The exploit leveraged a critical oversight in 4chan’s file validation system, allowing attackers to upload PostScript files containing malicious drawing commands disguised as legitimate PDFs.

According to cybersecurity experts analyzing the hack, these PostScript files were then processed by Ghostscript, a software used by 4chan to generate thumbnail images.

The site reportedly uses a severely outdated version of Ghostscript from 2012, which contains known vulnerabilities1. From this initial foothold, the attackers exploited what they described as “a mistaken suid binary” to elevate their privileges to that of the global user, effectively gaining complete control of the server.

The hackers claim to have maintained access to 4chan’s systems for over a year before executing the attack. The breach resulted in the complete extraction of 4chan’s PHP source code, including the main file “yotsuba.php” that manages posting and reporting functions.

Additionally, the email addresses and contact information of approximately 218 moderators, administrators, and “janitors” (lower-level moderators) were exposed.

As proof of their control over the system, the hackers temporarily restored a previously banned board called “/qa/” and defaced it with the message “U GOT HACKED XD”. This action confirmed they had gained administrative privileges within the system.

A group associated with rival imageboard Soyjak Party (colloquially known as “Sharty”) claimed responsibility for the attack. In a post on their platform, they stated: “Today, April 14, 2025, a hacker, who has been in 4cuck’s system for over a year, executed the true operation soyclipse”.

Security researchers noted that 4chan’s outdated technical infrastructure made it particularly vulnerable. “The hack was likely caused by 4chan using an extremely out-of-date version of PHP that has a lot of vulnerabilities and exploits and is using deprecated functions to interact with [their] MySQL database,” reported security researcher Yushe.

The hack has raised serious concerns about user privacy. While 4chan provides its users anonymity, the site collects IP addresses4. With admin panels compromised, unauthorized parties could access this data.

As of this writing, 4chan remains only intermittently accessible as administrators attempt to mitigate the damage. The exposure of moderator emails potentially compromises the anonymity that 4chan has long promised, with some leaked addresses reportedly including .edu and .gov domains.

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