CVE-2026-60008 in Gitea
Summary
by MITRE • 10/15/2026
Gitea's Jupyter notebook renderer inserts the notebook's language_info.name metadata into a CSS class attribute while disabling sanitization and rendering directly in the main document without an iframe sandbox. A malicious repository notebook can supply multiple CSS classes that create a viewport-covering overlay and intercept clicks when another user views it. The reported impact is UI redress; script execution was not demonstrated.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Gitea's Jupyter notebook renderer represents a significant security flaw rooted in improper input validation and insecure rendering practices. Specifically, the application takes the language_info.name metadata field from a submitted Jupyter notebook file and directly injects its value into a CSS class attribute within the HTML document structure. This operation is performed without any sanitization of the input data, allowing an attacker to supply arbitrary strings that are interpreted as valid CSS classes by the browser's rendering engine. Furthermore, the renderer displays this content in the main document context rather than isolating it within an iframe sandbox or a similarly restricted environment. This architectural decision removes critical security boundaries that would otherwise limit the scope of any malicious code execution or DOM manipulation attempts.
The operational impact of this flaw is primarily centered on UI redress attacks, also known as clickjacking variants enabled through CSS injection. By supplying carefully crafted values for the language_info.name field, an attacker can define multiple CSS classes that manipulate the visual presentation and interaction layer of the rendered notebook page. These malicious styles can create a viewport-covering overlay element with high opacity or z-index positioning that sits invisibly over legitimate interface elements such as buttons, links, or input fields. When another user views this compromised repository content in their browser, any clicks intended for the underlying application functionality are intercepted by the attacker-controlled overlay. This mechanism allows an adversary to trick users into performing unintended actions without their explicit consent, effectively hijacking the user's interaction with the platform.
From a technical classification perspective, this vulnerability aligns closely with CWE-79, which covers Cross-Site Scripting (XSS), specifically in its reflected or stored variants where untrusted data is used to construct HTML attributes. However, given that script execution was not demonstrated and the primary vector involves CSS manipulation for UI deception, it also strongly correlates with CWE-829, Inclusion of Functionality from Untrustworthy Control, as well as aspects of CWE-1021, Improper Restriction of Rendered UI Layers or Frames. The lack of an iframe sandbox further exacerbates the risk by violating principles outlined in ATT&CK technique T1566.002, Phishing: Spearphishing Attachment, where malicious content is delivered via a trusted vector to deceive users into interacting with it. Although the immediate impact does not include arbitrary code execution or data exfiltration through script injection, the ability to manipulate UI elements poses a severe threat to user integrity and trust in the platform's interface.
Mitigation strategies must focus on strict input validation and secure rendering contexts. The most effective remediation involves implementing robust sanitization of all metadata fields before they are inserted into HTML attributes or CSS classes. This includes whitelisting allowed characters for language identifiers and rejecting any values that contain special symbols, spaces, or sequences commonly used in CSS injection attacks such as semicolons, braces, or quotes. Additionally, the rendering engine should be configured to isolate notebook content within an iframe with a sandbox attribute that restricts script execution and interaction capabilities unless explicitly permitted by trusted sources. Implementing Content Security Policy headers can also help mitigate potential downstream effects by limiting where stylesheets and scripts can originate from. Regular security audits of the renderer component are recommended to ensure that future updates do not reintroduce similar flaws in how user-supplied data is processed and displayed.