From November 8 to 9, two completely different but mutually reflecting security incidents exposed the vulnerabilities of crypto infrastructure: on one hand, decentralized exchange Arcus disclosed on November 9 that an accounting vulnerability had been exploited, allowing the recorded balance of operational accounts to exceed the actual held assets, ultimately creating a gap of about 2.23 million USDG within the system; reportedly, the attacker attempted to withdraw about 3 million USD but failed to transfer all at once due to the cross-chain bridge's rate limiting mechanism. Arcus subsequently announced that company funds would be used to fully cover the gap, emphasizing that other user accounts were not directly affected. On the other hand, the Lightning Network wallet system LNbits admitted on November 8 that there was a vulnerability affecting all wallet versions prior to 1.7.0, directly categorizing it as "old version funds facing theft risk." An urgent security update of 1.7.0 was released, requiring operators to upgrade and migrate to a new server environment, while reminding that if credentials were leaked before the upgrade, attackers might retain access after the upgrade, necessitating additional operations such as credential rotation and access auditing to truly eliminate threats. One case reflects the logic of using treasury funds to cover internal losses after the incident, while the other emphasizes narrowing the attack surface as much as possible through patches and operations beforehand. Both cases outline the inescapable security game between post-incident bailouts and preemptive protection in current crypto infrastructure.

Arcus Accounting Vulnerability: Inflated Balances Leading to a 2.23 Million Gap

Returning to the Arcus case, the project team defined this incident on November 9 as an "accounting vulnerability," rather than the traditional sense of a smart contract being hacked. According to the official statement, there exists a type of operational account in the system whose accounting method allows the recorded balance to exceed the actual deposited assets, effectively creating a gray area where inner accounts can artificially "inflate their balances." Normally, such accounts should only be used for internal operations and fund dispatch, but once an attacker realizes the misalignment between accounting rules and actual assets, it is equivalent to discovering an entry point to create "phantom balances" within the system.

The process of exploiting the vulnerability thus began: the attacker first used this accounting logic to generate a recorded balance far exceeding real assets within the system, then proceeded to initiate withdrawals according to the usual process, ultimately tearing open a gap valued at approximately 2.23 million USDG between the recorded and on-chain assets. It is noteworthy that after completing this gap, the attacker did not stop there but further requested withdrawals of about 3 million USD; what truly blocked this step was not risk control at the application layer but the rate limitation mechanism of the cross-chain bridge, which strictly limited withdrawal speed, preventing the release of larger amounts of funds in a short time. Arcus emphasized in its explanation that except for this internal loss covered by the company treasury, other user accounts did not experience direct financial losses, thereby locking the nature of the incident within the realm of "a treasury covering an accounting gap."

Arcus Treasury Coverage and Rate Limitation Defense

The gap of approximately 2.23 million USDG left behind after the vulnerability was exploited was not "distributed" at the user level but was directly classified by Arcus as an operational risk, with the company treasury stepping in to fully cover it. The official statement repeatedly emphasized that "it did not affect other user accounts," effectively locking this loss within the scope of the project team's own responsibility: on one side were the inflated recorded balances of operational accounts due to accounting vulnerabilities, and on the other side was the treasury's real assets used to fill the gap, with the divide crossed by Arcus's own funds. The choice to use treasury coverage firstly indicates that the project team did have available funds as a buffer, and secondly serves as a stance—amid incidents caused by technical and procedural errors, the team is willing to confine responsibility at the company level rather than allowing on-chain risks to naturally flow down to all participants according to the contract logic.

Equally critical as treasury coverage is the "passive defense" of the cross-chain bridge's rate limitation in this incident. After creating the gap, the attacker attempted to initiate a withdrawal of about 3 million USD. If the cross-chain bridge had no throttling design for cross-chain funds and withdrawals, this money could have been transferred in a very short time. However, the reality is that the rate limitation mechanism forced the withdrawals to be redirected, preventing the attacker from extracting all target funds within a single time window, giving the project team space to handle the situation. This detail transforms what is often viewed as a "compromise in experience" into a genuine safety valve. From the perspective of DeFi governance and user trust, this emergency response plan also exposes a long-term tension: on one hand, the central treasury covering can quickly stabilize the situation during an incident, protecting individual accounts from direct impact; on the other hand, it means that the last layer of risk management is controlled by a few entities' funds and decisions, forming an irreconcilable compromise between the ideal of decentralization and the reality of fault tolerance mechanisms.

LNbits Vulnerability Affecting Old Versions: The 1.7.0 Upgrade Race

Almost a day before Arcus announced its treasury coverage, the Lightning Network wallet system LNbits was also forced to hit the "emergency brake." On November 8, LNbits officially disclosed a security vulnerability and explicitly named: all versions prior to 1.7.0 were within the impact scope. The wording was unequivocal—funds hosted in old version instances were directly defined as "facing theft risk," which meant the problem was no longer an incidental defect of a specific release but that the entire version line was marked as an unsafe environment.

In this alert, 1.7.0 was positioned as a "security update" rather than a regular iteration. The official required operators not only to complete the software upgrade as soon as possible but also to migrate services to a new server environment to completely cut off potential attack paths. LNbits repeatedly emphasized the time sensitivity, issuing near-command reminders: delaying the upgrade equates to creating a window for attackers, especially for those deployments where credential leaks have already occurred, which must be paired with credential rotation and access auditing to ensure the upgrade is truly effective. With the announcement issued, those still running old versions of LNbits were collectively pushed into a race to upgrade that could afford no absence, making security the first commitment to be fulfilled in all operational strategies.

The Shadow of Leaked Credentials over Lightning Network Operational Risks

LNbits pointed out a fact in the announcement that made it difficult for operators to easily rest easy: even after upgrading to 1.7.0, previously leaked keys, tokens, or API credentials could still allow attackers to maintain access in the new version. The jump in version number does not automatically invalidate these "old keys," meaning the attack path has not been completely severed, which directly shatters many people's technical fantasy of simply "patching it up and being worry-free."

For nodes and service providers operating Lightning Network wallets, LNbits' reminder raised the issue to a systemic risk at the operational level: the funds rely on more than just code logic; there are also access control elements scattered across various servers, scripts, and integrated services. The official suggestion to migrate to a new server essentially urges operators to redeploy the entire environment and access policies, rather than simply overlaying the new version on top of the existing infrastructure, which may have been previously inspected. Credential leaks often transcend single vulnerability events and have a continuity over time; if key rotation, cleaning up old tokens, and auditing access logs are not simultaneously completed outside of the upgrade actions, this vulnerability could transform from a simple "bug fixing" incident into a long-term inquiry into whether overall operational security is qualified.

Arcus and LNbits Reflecting Weaknesses in Crypto Security

The accounting vulnerability of Arcus and the wallet vulnerability of LNbits occurred around the same time, one involving the accounting logic at a DeFi exchange, the other exposing operational issues in the Lightning Network wallet, collectively bringing the long-ignored "non-pure contract bugs" to the forefront of the industry. In the Arcus incident, the operational accounts could "record" balances exceeding the actual holdings on paper, ultimately leading to a gap of about 2.23 million USDG, while the attacker attempted to withdraw about 3 million USD but was held back by the cross-chain bridge's rate limitation mechanism, with the remaining loss wholly covered by the company's treasury; LNbits, on the other hand, chose to release the 1.7.0 security update when vulnerabilities existed in the old version wallet that could lead to theft of funds, requiring operators to upgrade and migrate to new servers and reminding that any leaked credentials prior to this must be addressed through key rotation and access auditing to truly eliminate hazards. The former uses centralized treasury to absorb a one-time accounting gap, while the latter reduces future risks through mandatory upgrades and environment rebuilding. Both response paths emphasize "fund security" from the user perception standpoint, but the long-term effectiveness depends on how the community views the sustainability of treasury coverage and whether node operators genuinely implement upgrades, migrations, and credential cleanups. Returning to security itself, these two incidents remind the market that audits cannot only focus on contract functions and code lines but must also systematically examine architectural risks such as accounting logic, permission design, and rate limitations. Continuous tracking of LNbits upgrade execution, standardization of operations, and whether treasury coverage models like Arcus can complement more stringent preemptive audits may truly solidify this security line before the next wave of attacks arrives.

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