The 2025 4chan Hack: How a Simple PDF Upload Took Down the Web’s Most Infamous Anonymous Imageboard

Patrick_Yu

What is 4chan?

4chan is an anonymous English-language imageboard website launched on October 1, 2003, by then-15-year-old Christopher Poole, known online as "moot." Inspired by the Japanese imageboard Futaba Channel (2chan), 4chan was initially created as a space for Western anime and manga enthusiasts. Over time, it evolved into a vast and unfiltered forum encompassing a wide array of topics, including video games, politics, technology, and more.

The platform is structured into various boards, each dedicated to specific subjects. Users typically post anonymously, fostering a culture where content is judged on its merit rather than the identity of the poster. This anonymity has been both a defining feature and a source of controversy, as it allows for free expression but also enables the spread of offensive content.​ 4chan has also been instrumental in the creation and dissemination of numerous internet memes and trends.

A brief history of 4chan

https://www.youtube.com/watch?v=dQw4w9WgXcQ

The Early Years

Christopher Poole founded 4chan in 2003, drawing inspiration from Japanese imageboards and the online community of Something Awful. The site began with a focus on anime and manga but quickly expanded to include a multitude of boards covering diverse topics. One of the most notorious boards, /b/ (Random), became known for its anything-goes policy, leading to a mix of creativity and chaos.​

Notable Incidents

Over the years, 4chan has been at the center of several high-profile incidents:​

• Rickrolling (2007): 4chan users initiated the "Rickroll" meme by tricking others into clicking links that led to Rick Astley's 1987 hit "Never Gonna Give You Up." This bait-and-switch prank became a widespread internet phenomenon.
• Steve Jobs Death Hoax (2008): A false rumor about Apple's CEO Steve Jobs suffering a heart attack originated on 4chan, leading to a significant drop in Apple's stock price before the rumor was debunked.​
• Pitbull to Alaska (2012): In response to a Walmart promotion to bring rapper Pitbull to the store with the most votes, 4chan users orchestrated a campaign to send him to the most remote location possible, Kodiak, Alaska. The campaign succeeded, and Pitbull honored the results by performing there. ​

Ownership Changes

In January 2015, Poole stepped down as the site's administrator, citing the stress of managing the platform. Later that year, he sold 4chan to Hiroyuki Nishimura, the founder of 2channel, the Japanese message board that had originally inspired 4chan. Nishimura's acquisition aimed to bring experienced leadership to the site, given his background in managing large online communities.​

The recent 4chan hack: A breakdown

On April 14, 2025, the notoriously anonymous platform 4chan was hacked through a critical vulnerability involving PDF file uploads. Attackers exploited outdated and insecure software handling PDF files, allowing them to gain remote code execution and ultimately escalate privileges to obtain full administrative access to 4chan’s servers. This breach led to significant data exposure, including sensitive user and administrative information.

1. Who Did It?

Reports of a possible breach surfaced when users noticed unusual activity on 4chan, including the brief reappearance of a previously banned board. Shortly after, the site was defaced with the mocking message: “U GOT HACKED XD.” Further evidence of a breach emerged when a rival forum, Soyjak.party, began posting screenshots allegedly showing 4chan’s internal administrative systems and databases.

Soyjak.party, a splinter community formed from the remnants of 4chan’s defunct /qa/ board, later confirmed their involvement. The group, which had longstanding grievances against 4chan’s moderation team, appeared motivated by a desire to expose and embarrass site administrators.

Screenshots from the alleged hack indicated substantial access to sensitive internal information, including administrator usernames, email addresses, user IP addresses, deleted posts, and even internal documentation. The situation escalated further as Soyjak.party members shared personal details, or "doxes," of purported 4chan administrators and moderators.

2. How the Breach Occurred

Certain 4chan boards—such as /gd/, /po/, /qst/, /sci/, and /tg/—allowed users to upload PDF files. However, the platform failed to verify that uploaded files were genuine PDFs. This oversight permitted attackers to upload malicious PostScript files disguised with a .pdf extension.​

These files were processed by Ghostscript, a tool used to generate thumbnails for uploaded documents. Unfortunately, 4chan was utilizing a version of Ghostscript from 2012, which contained known vulnerabilities. By exploiting these vulnerabilities, the attacker achieved remote code execution on the server.​

Subsequently, the attacker leveraged a misconfigured SUID (Set User ID upon execution) binary to escalate privileges, gaining root access to the server. This level of access allowed the attacker to exfiltrate sensitive data, including 4chan's source code, internal logs, and administrative information. ​

3. Aftermath

The severity of the breach prompted an immediate and comprehensive response from 4chan administrators. The site was temporarily taken offline to mitigate further damage and thoroughly investigate the vulnerabilities. During this downtime, administrators patched identified weaknesses, removed PDF upload capabilities, updated internal systems, and reinforced security protocols to prevent similar incidents in the future.

4. Is 4chan Back Up?

As of April 27, 2025, 4chan has returned online with limited functionality and enhanced security measures. PDF uploads remain disabled permanently, and certain vulnerable or controversial boards have been removed. While the technical recovery has been successful, the breach has profoundly impacted user trust and raised ongoing concerns about the platform's security and future sustainability. Administrators continue to monitor the site closely to ensure its stability and security moving forward.

Conclusion

The recent hack on 4chan serves as a stark reminder of how even longstanding internet platforms can fall victim to neglected infrastructure and outdated security practices. By exploiting a vulnerability in the site’s PDF upload system, attackers were able to access sensitive internal data and expose many of the administrators behind the platform’s veil of anonymity. 

Although 4chan has since restored basic functionality and implemented new security measures, the breach has deeply shaken its user base and highlighted systemic weaknesses. It also reinforces a broader lesson: users should never place personal or sensitive information on anonymous platforms like 4chan or Reddit, where even a small lapse in security can have massive consequences. 

Moving forward, 4chan faces the difficult task of rebuilding trust and proving that it can still operate as a platform for anonymous free expression without compromising the safety of its users and staff.