CVE-2025-56683 is a cross-site scripting (XSS) vulnerability affecting Logseq version 0.10.9, specifically within the /app/marketplace.html component. The vulnerability arises because the application improperly sanitizes or fails to sanitize JavaScript embedded within README.md markdown files loaded in the marketplace interface. An attacker can craft a malicious README.md file containing arbitrary JavaScript code that executes when a user views the file in Logseq. This execution occurs in the context of the user's browser session, potentially allowing the attacker to steal session tokens, manipulate the user interface, or perform actions on behalf of the user. The vulnerability does not require prior authentication, but exploitation requires user interaction—namely, opening or viewing the malicious README.md file. No CVSS score has been assigned yet, and no public exploits have been reported. The lack of patch links suggests that a fix may not yet be available, emphasizing the need for caution. This vulnerability highlights the risks of rendering untrusted markdown content without proper sanitization in desktop or web applications. Given Logseq's use in knowledge management and note-taking, sensitive organizational data could be exposed if exploited.

For European organizations, exploitation of this XSS vulnerability could lead to significant confidentiality and integrity risks. Attackers could hijack user sessions, steal sensitive data such as internal notes or credentials, or inject further malicious payloads to escalate attacks within the network. Since Logseq is often used for knowledge management, intellectual property and internal communications could be compromised. The vulnerability could also facilitate phishing or social engineering attacks by manipulating the user interface. While availability impact is limited, the breach of trust and data confidentiality could have regulatory implications under GDPR, leading to legal and financial consequences. Organizations relying on Logseq for collaborative work or storing sensitive information are particularly at risk. The absence of a patch increases exposure time, and the ease of exploitation through crafted markdown files heightens the threat level.

Organizations should immediately restrict or disable the use of the marketplace feature in Logseq until a patch is released. Users should be educated not to open README.md or other markdown files from untrusted sources within Logseq. Implementing additional input sanitization or filtering at the application or network level can help block malicious JavaScript payloads embedded in markdown files. Monitoring logs for unusual activity related to the marketplace component and suspicious file uploads is advised. If possible, run Logseq in isolated environments or sandboxes to limit potential damage. Organizations should track updates from Logseq developers and apply security patches promptly once available. Additionally, integrating endpoint protection solutions that detect script injection or anomalous browser behavior can provide an extra defense layer.