CVE-2025-53831: Stored XSS in DrawIO for ownCloud (CVSS 8.2 HIGH)

Technical summary

CVE-2025-53831 is a stored XSS vulnerability (CWE-79) in DrawIO for ownCloud caused by improper neutralization of user input during HTML generation. The flaw allows authenticated attackers to inject arbitrary JavaScript that persists in the application's data store. When subsequent users access the compromised drawing or document, the malicious script executes in their browser context with their session privileges. The vulnerability affects DrawIO for ownCloud prior to version 1.0.2 and ownCloud 10 prior to version 10.15.3. The CVSS 3.1 score of 8.2 (HIGH) reflects network accessibility, low attack complexity, and the requirement for user interaction from a victim—combined with cross-site impact and potential for confidentiality breach.

Business impact

A successful exploit could allow attackers to steal session tokens, modify documents, redirect users to malicious sites, or harvest credentials from users who view compromised drawings. In collaborative environments where DrawIO is used for documentation, architecture diagrams, or design sharing, a single malicious upload by a compromised or rogue account could affect multiple team members. Organizations relying on ownCloud for file management and DrawIO for visual collaboration face data integrity concerns and potential lateral movement opportunities if accounts are compromised through this vector.

Affected systems

The vulnerability impacts DrawIO for ownCloud versions prior to 1.0.2, which runs on ownCloud 10 versions prior to 10.15.3. Any deployment of DrawIO integrated with affected ownCloud 10 instances is at risk. Organizations using DrawIO standalone or with other ownCloud versions (e.g., ownCloud Infinite Scale) should verify their specific configurations against vendor advisories. The vulnerability requires the attacker to have pre-existing access to the DrawIO application, limiting the attack surface to authenticated users or compromised accounts with DrawIO permissions.

Exploitability

Exploitation requires authentication to the DrawIO application, which restricts attacks to users with valid credentials or those who have compromised an account. The attack complexity is low—an attacker simply needs to craft a malicious drawing or document containing XSS payload and save it. No special tools or techniques are required. The user interaction requirement (a victim must view the malicious content) is a practical constraint, though in collaborative environments this is highly likely. The vulnerability is not currently tracked on CISA's Known Exploited Vulnerabilities catalog, suggesting active exploitation in the wild has not been publicly disclosed, though the HIGH severity and straightforward exploitation path warrant swift patching.

Remediation

Organizations should prioritize updating DrawIO for ownCloud to version 1.0.2 or later, or upgrading ownCloud 10 to version 10.15.3 or later. If immediate patching is not feasible, consider restricting access to DrawIO to trusted users, disabling the app until patched, or isolating DrawIO instances from sensitive workflows. Input validation and output encoding improvements in the patched versions mitigate the XSS injection vector. Verify patch deployment by confirming version numbers in the ownCloud admin interface.

Patch guidance

Patch DrawIO for ownCloud by upgrading to version 1.0.2 or later. Alternatively, upgrade ownCloud 10 to version 10.15.3 or later, which includes the fixed DrawIO component. Consult the ownCloud and DrawIO official release notes to confirm patch availability for your specific deployment. Test patches in a non-production environment before rollout. After patching, consider clearing browser caches and sessions to invalidate any cookies or tokens that may have been exposed prior to remediation. Monitor ownCloud logs for signs of XSS injection attempts during the vulnerability window.

Detection guidance

Review ownCloud and DrawIO logs for unusual drawing or document creation activity, particularly by service accounts or users with unusual access patterns. Look for HTML or JavaScript payloads in stored drawing files—audit exported or backup DrawIO content for suspicious script tags or event handlers. Monitor web traffic to DrawIO endpoints for anomalous requests or response sizes that might indicate XSS payload delivery. Browser developer console errors or warnings when opening drawings may signal malicious script execution. Implement WAF rules to block common XSS patterns in DrawIO API parameters if running behind a web application firewall.

Why prioritize this

This vulnerability merits HIGH priority due to its HIGH CVSS score (8.2), the cross-site impact enabling broad user compromise, and the low barrier to exploitation for any authenticated attacker. DrawIO is often used in collaborative, multi-user environments where a single malicious document can compromise multiple stakeholders. While the KEV catalog does not yet list active exploitation, the simplicity of the attack and the sensitive nature of architectural or design diagrams (which often contain IP or infrastructure insights) justify immediate patching. Organizations with large ownCloud deployments or heavy DrawIO usage should treat this as urgent.

Risk score, explained

The CVSS 3.1 score of 8.2 (HIGH) reflects: (1) Network vector—the app is accessible over the network; (2) Low attack complexity—no special conditions required; (3) Low privileges—requires only basic user access to DrawIO; (4) User interaction required—victim must view the malicious content; (5) Scope changed—the attack can impact resources beyond the vulnerable component (other users' browsers and sessions); (6) High confidentiality impact—session tokens or data can be stolen; (7) Low integrity and availability impact—the focus is on script injection rather than data destruction. The score appropriately captures the threat to multi-user environments while acknowledging that exploitation requires prior authentication.

Frequently asked questions