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DOM XSS in Apryse WebViewer via remote uiConfig (CVE-2025-70402)
CVE-2025-70402 is described as a critical DOM-based cross-site scripting vulnerability in Apryse WebViewer (formerly PDFTron) where the uiConfig query parameter is trusted as a remote URL, fetched, parsed as JSON, and applied to the WebViewer UI. A malicious value in a uiConfig field (described as a “glyph” field) is propagated into a React component (Icon.js) and rendered via dangerouslySetInnerHTML without sanitization, enabling script execution in the context of the WebViewer origin. The disclosure notes an SVG <foreignObject> technique to achieve script execution as a bypass despite DOMParser behavior when handling image/svg+xml.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation results in arbitrary JavaScript execution in the victim’s browser within the security context of the affected WebViewer deployment. The source material claims this was leveraged in at least one client proof-of-value engagement to achieve one-click account takeover (i.e., session/token theft or equivalent account compromise via XSS).
If you can’t patch tonight, do this now.
Until patched, restrict or disable remote uiConfig loading (do not allow uiConfig to reference arbitrary remote URLs). Enforce a strict Content Security Policy (CSP) appropriate for the deployment to reduce XSS exploitability, and validate/allowlist any configuration sources and fields before applying them to the UI.
Patch, then assume compromise.
Apply Apryse-provided patches/updates that address CVE-2025-70402 by removing/locking down remote uiConfig loading and/or ensuring untrusted uiConfig-derived fields are not rendered with dangerouslySetInnerHTML without robust sanitization. Ensure the vulnerable UI rendering path (Icon.js) no longer inserts attacker-controlled markup.
No public exploits tracked yet. Mallory keeps watching.
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.