CVE-2025-59038 is a high-severity vulnerability affecting Prebid.js version 10.9.2, an open-source JavaScript library widely used by online publishers to implement header bidding for programmatic advertising. The vulnerability is classified under CWE-506, which pertains to embedded malicious code. In this case, the malicious code was introduced into the Prebid.js 10.9.2 release, potentially via a supply chain compromise or unauthorized code injection. The embedded malware attempts to intercept and redirect cryptocurrency transactions initiated on websites using the compromised library version, diverting funds to attacker-controlled wallets. This attack vector leverages the trust publishers place in Prebid.js as a third-party dependency, allowing attackers to manipulate client-side transaction flows without requiring user authentication or elevated privileges. The vulnerability does not require prior authentication but does require user interaction, as the malicious code activates during normal site use involving crypto transactions. The issue was resolved in Prebid.js version 10.10.0, with a recommended workaround to downgrade to version 10.9.1, which is unaffected. The CVSS 4.0 base score of 8.6 reflects the network attack vector, low attack complexity, no privileges required, but user interaction needed, and high impact on confidentiality, integrity, and availability of the affected systems. No known exploits have been reported in the wild as of the publication date, but the potential for financial theft and reputational damage is significant given the nature of the targeted transactions and the widespread use of Prebid.js in the digital advertising ecosystem.

European organizations relying on Prebid.js 10.9.2 for header bidding in their web properties face significant risks from this vulnerability. The primary impact is financial loss through redirected cryptocurrency transactions, which can directly affect e-commerce platforms, financial services, and any online business accepting crypto payments. The integrity of transaction data is compromised, undermining trust in the affected websites. Additionally, the presence of malicious code can lead to reputational damage, regulatory scrutiny under GDPR due to potential unauthorized data manipulation, and increased operational costs for incident response and remediation. Since Prebid.js is commonly used by digital publishers and advertising platforms, media companies and online marketplaces in Europe are particularly vulnerable. The attack does not require authentication but depends on user interaction, meaning end-users engaging in crypto transactions are at risk. The widespread adoption of Prebid.js in Europe, combined with the growing use of cryptocurrencies, amplifies the threat's potential impact across multiple sectors.

European organizations should immediately verify their use of Prebid.js and identify any instances of version 10.9.2 in their web environments. The primary mitigation is to upgrade to Prebid.js version 10.10.0, which contains the fix for this vulnerability. If immediate upgrading is not feasible, downgrading to version 10.9.1 is a viable temporary workaround. Organizations should audit their supply chain and code repositories to ensure no unauthorized code persists. Implementing strict integrity checks such as Subresource Integrity (SRI) for JavaScript libraries can prevent tampered scripts from loading. Monitoring outgoing crypto transaction endpoints for anomalies or unexpected redirects can help detect exploitation attempts. Additionally, web application firewalls (WAFs) should be configured to detect and block suspicious script behaviors related to transaction redirection. Educating developers and security teams about supply chain risks and enforcing secure development lifecycle practices will reduce future exposure. Finally, organizations should review their incident response plans to address potential financial fraud stemming from this vulnerability.