CVE-2026-78391 in RansomLook
Summary
by MITRE • 08/24/2026
RansomLook contains a stored cross-site scripting (XSS) vulnerability in the cryptocurrency wallet detail view. Cryptocurrency addresses and blockchain names originating from external sources, including the public crowd-sourced ransomwhe.re feed, were stored without sufficient validation and later embedded directly into an inline JavaScript onclick handler.
Although Jinja HTML autoescaping was applied, it does not provide adequate protection when untrusted data is inserted into a JavaScript string inside an HTML attribute. HTML entities such as ' are decoded by the browser's HTML parser before the resulting attribute is interpreted as JavaScript. Consequently, a specially crafted cryptocurrency address containing quote characters and JavaScript syntax could escape the intended string literal and execute arbitrary JavaScript when a user clicked the affected wallet's CSV export button.
Because cryptocurrency information imported from an untrusted upstream could reach the vulnerable rendering path, exploitation may not require an authenticated RansomLook account if an attacker can introduce a malicious wallet record into a consumed external data source. Successful exploitation could allow attacker-controlled JavaScript to execute in the security context of the RansomLook web application, potentially exposing information accessible to the victim or performing actions with the victim's privileges.
The patch mitigates the issue by validating cryptocurrency addresses and blockchain identifiers before storage, restricting them to a safe character set, and replacing the inline JavaScript handler with data-* attributes and an external event listener so wallet values are treated strictly as data rather than executable JavaScript.
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Analysis
by VulDB Data Team • 08/24/2026
RansomLook is susceptible to a stored cross-site scripting vulnerability within its cryptocurrency wallet detail view functionality. This security flaw arises from the application's handling of untrusted input derived from external sources, specifically including public crowd-sourced feeds such as ransomwhe.re. When users import or interact with data originating from these upstream providers, the system stores cryptocurrency addresses and blockchain names without implementing sufficient validation mechanisms to sanitize potentially malicious content. The core technical deficiency lies in how this stored data is subsequently rendered within the application's interface. Specifically, the vulnerable code embeds user-controlled values directly into an inline JavaScript onclick handler attribute of HTML elements. This architectural decision creates a direct pathway for script injection if the input contains characters that can break out of the intended string context.
The vulnerability exploits a specific behavior in web browser rendering engines regarding how HTML entities are processed before being interpreted as executable code. Although RansomLook utilizes Jinja2 with its default autoescaping feature, this protection is insufficient for data embedded within JavaScript strings inside HTML attributes. The browser's HTML parser decodes HTML entity sequences, such as the single quote character represented by ', prior to passing the attribute value to the JavaScript engine. Consequently, an attacker can craft a malicious cryptocurrency address that includes encoded quotes and other JavaScript syntax elements. When this crafted data is stored in the database and later rendered on the page, the browser decodes the entities into their literal characters. This decoding allows the injected payload to escape the surrounding string literals defined by the inline onclick handler, thereby breaking out of the intended context and executing arbitrary JavaScript code within the application's security domain.
The operational impact of this vulnerability is significant due to its stored nature and potential for exploitation without authentication. Because the malicious data originates from an external feed that the application consumes automatically or semi-automatically, an attacker does not necessarily need a valid RansomLook account to trigger the initial injection phase. By introducing a specially crafted wallet record into the upstream ransomwhe.re feed or any other consumed source, the attacker ensures that their payload is stored in the database and served to victims upon viewing the affected wallet details. The execution of arbitrary JavaScript occurs when an authenticated user interacts with the interface, specifically by clicking the CSV export button associated with the compromised wallet entry. This interaction triggers the malicious onclick handler, leading to code execution in the context of the RansomLook web application.
Successful exploitation allows an attacker to perform actions with the victim's privileges and access sensitive information available within that security context. Potential consequences include session hijacking through cookie theft, defacement of the user interface, or performing unauthorized operations on behalf of the victim such as exporting data or modifying settings. This aligns with common vulnerability classifications found in industry standards. The flaw corresponds to CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. Furthermore, from a tactical perspective related to the MITRE ATT&CK framework, this vulnerability facilitates initial access and potentially credential harvesting or data exfiltration through techniques associated with client-side code injection. The stored nature of the XSS means that every user viewing the compromised page is at risk, amplifying the blast radius beyond just the individual who imported the malicious feed item.
To mitigate this vulnerability, developers have implemented a multi-layered defense strategy focusing on both input validation and output encoding architecture changes. First, strict input validation has been introduced for cryptocurrency addresses and blockchain identifiers before they are persisted to storage. This validation restricts accepted characters to a safe whitelist, effectively preventing the injection of special symbols like quotes or semicolons that could facilitate script execution. Second, the application's frontend architecture was refactored to eliminate inline JavaScript event handlers entirely. The vulnerable onclick attributes were replaced with data-* attributes, which store values strictly as inert data rather than executable code. An external event listener is now responsible for handling user interactions such as clicking the export button. This separation of logic and presentation ensures that even if malicious characters are present in the stored data, they cannot be interpreted as JavaScript commands because they are never embedded directly into script contexts by the server-side rendering engine.