A major security breach linked to Cardex, a blockchain-based game on AbstractChain, has led to an estimated $400,000 in losses after attackers exploited a session key vulnerability.
The breach, which surfaced on Tuesday, impacted thousands of wallets that had previously interacted with the game. AbstractChain confirmed the issue in an initial post-mortem, clarifying that the exploit was not a flaw in its network or wallet infrastructure, but rather a security lapse on Cardex’s front-end.
How Did the Exploit Happen?
The incident, described as a “session key hack”, allowed a malicious actor to gain unauthorized access to users’ wallets. Once inside, they drained funds by executing transactions that the victims had unknowingly approved.
Despite the severity of the breach, the Abstract team, along with security researchers and Seal 911, responded swiftly, containing the attack and preventing further unauthorized access.
Root Cause: Cardex’s Poor Session Key Management
According to Cygaar, a pseudonymous contributor to Abstract, the exploit stemmed from improper session key management by Cardex. Session keys are temporary permissions that allow applications to interact with wallets in a limited capacity.
If not properly configured, they can leave users vulnerable to malicious activity—which is exactly what happened in this case.
The Cardex front end mistakenly exposed the private key of its session signer, a critical security lapse that allowed an attacker to execute unauthorized transactions on behalf of users.
Additionally, Cardex made the risky decision to use the same session signer for all users, further compounding the problem.
While the Cardex smart contracts were vetted by auditors and remained secure, this front-end oversight meant that even verified applications can still pose risks if their security practices are not stringent.
Also Read: Clipper DEX Clarifies Security Breach, Confirms API Vulnerability Behind $450,000 Exploit
Abstract’s Response and Security Measures
AbstractChain has distanced itself from direct responsibility, emphasizing that the issue was specific to Cardex and did not stem from its network or wallet infrastructure. However, the team has vowed to tighten security measures to prevent similar incidents in the future.
The company outlined its current security standards, which include mandatory security audits, direct onboarding with teams, and continuous collaboration with developers on best security practices.
The breach has prompted further discussions on how blockchain ecosystems can better manage third-party integrations, ensuring that individual applications do not become weak links in otherwise secure networks.
As an immediate safety measure, Abstract has advised all users to revoke any approvals or permissions they may have given to Cardex.
Industry Reactions and Future Implications
The breach has reignited concerns about the security of blockchain applications, particularly those relying on session keys for user interaction.
Security experts have pointed out that while AbstractChain’s core infrastructure remained uncompromised, the exploit demonstrates how weak third-party integrations can still pose a major risk.
The response from AbstractChain has been largely praised for its transparency and quick action. Unlike traditional crisis management strategies that rely on marketing teams, Abstract allowed its engineers to directly engage with the community, providing technical breakdowns and real-time updates on the situation.
This approach has helped reassure some users, though others remain cautious about potential future vulnerabilities.
The Cardex exploit serves as a stark reminder that even well-audited platforms can suffer breaches due to human error or poor implementation of security practices.
Blockchain developers are now under increased pressure to enforce stricter oversight over third-party applications, ensuring that every aspect, from smart contracts to front-end code, is rigorously secured.