The amount of crypto  malware has doubled in the first quarter of 2025 as per research.

Kaspersky GReAT (Global Research and Analysis Team) experts have discovered open-source packages that download the Quasar backdoor and a stealer designed to exfiltrate cryptocurrency. The malicious packages are intended for the Cursor AI development environment, which is based on Visual Studio Code — a tool used for AI-assisted coding.

The fake extension, published under the name “Solidity Language,” had accumulated 54,000 downloads before being detected and removed.

What makes this attack particularly insidious is its exploitation of search ranking algorithms to position the malicious extension above legitimate alternatives.

How the Threat actors deceive the developers

During an incident response, a blockchain developer from Russia reached out to Kaspersky after installing one of these fake extensions on his computer, which allowed attackers to steal approximately $500,000 worth of crypto assets.

The threat actor behind these packages managed to deceive the developer by making the malicious package rank higher than the legitimate one. The attacker achieved this by artificially inflating the malicious package’s downloads count to 54,000.

After the malicious extension downloaded by the developer was discovered and removed from the repository, the threat actor republished it and artificially inflated its installation count to a higher number – 2 million, compared to 61,000 for the legitimate package.

The extension was removed from the platform following a request from Kaspersky.

The attackers leveraged the Open VSX registry’s relevance-based ranking system, which considers factors including recency of updates, download counts, and ratings. The attack infrastructure reveals a well-organized operation extending beyond this single incident.

In 2025, threat actors are actively publishing clones of legitimate software packages that, once installed, execute harmful payloads ranging from cryptocurrency theft to full codebase deletion.

The discovery leads us to think how cyber criminals take advantage of the trust inherent in open-source environments by embedding harmful code. All third-party code should be treated as untrusted until proven.

The threat actor behind these packages managed to deceive the developer by making the malicious package rank higher than the legitimate one. The attacker achieved this by artificially inflating the malicious package’s downloads count to 54,000.

After installation, the victim gained no actual functionality from the extension. Instead, malicious ScreenConnect software was installed on the computer, granting threat actors remote access to the infected device.

Using this access, they deployed the open-source Quasar backdoor along with a stealer that collects data from browsers, email clients, and crypto wallets. With these tools, the threat actors were able to obtain the developer’s wallet seed phrases and subsequently steal cryptocurrency from the accounts.

Mitigation Strategies from Intruceptlabs

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Source: https://www.kaspersky.com/about/press-releases/kaspersky-uncovers-500k-crypto-heist-through-malicious-packages-targeting-cursor-developers