VU#699627: Readwise Reader for Android, version 8.7.2, contains multiple XSS vulnerabilities

Overview

Three cross-site scripting (XSS) vulnerabilities identified in Readwise Reader for Android version 8.7.2 are disclosed. An attacker with the ability to craft malicious documents or metadata can exploit these vulnerabilities by supplying poisoned content that bypasses sanitization. Successful exploitation could allow the attacker to execute arbitrary JavaScript within the application’s WebView context and compromise the confidentiality and integrity of user data, including access to stored documents, credentials, and session tokens.

Description

Readwise Reader from Readwise is designed to provide a unified read-it-later service that helps individuals collect and organize articles, newsletters, videos, and other content of interest into a single reading interface. It is available on multiple platforms including Android and can synchronize content across devices.

CVE-2026-18311: A stored cross-site scripting (XSS) vulnerability in the header rendering component in Readwise Reader for Android version 8.7.2 allows remote attackers to execute arbitrary JavaScript via crafted document metadata fields. The header rendering component is impacted due to insufficient HTML escaping of metadata fields such as ‘doc.author’ and ‘doc.title’, which allows malicious scripts to be stored in the user’s library and synchronized to Android devices where they are executed in the WebView context.

CVE-2026-18312: A stored cross-site scripting (XSS) vulnerability in the WebView URL construction logic in Readwise Reader for Android version 8.7.2 allows remote attackers to execute arbitrary JavaScript via malicious URL metadata. The WebView URL construction for X (formerly Twitter) video fallback and iOS paywall messages is impacted due to improper escaping of URL metadata before interpolation into href attributes, which allows user-controlled values to break out of the URL structure and inject script elements that are inserted into the DOM via innerHTML.

CVE-2026-18320: A stored cross-site scripting (XSS) vulnerability in the article body sanitization component in Readwise Reader for Android version 8.7.2 allows remote attackers to execute arbitrary JavaScript via malicious SVG markup. The sanitize-html configuration is impacted due to a wildcard attribute rule that permits all attributes on SVG and PATH elements, which allows script-capable attributes such as onload and onerror to bypass sanitization.

Impact

An attacker with the ability to create or modify documents accessible to Readwise Reader can supply documents containing malicious metadata or markup that bypasses sanitization and is subsequently stored in users libraries. Because these documents are synchronized to Android devices and rendered within the Reader WebView, each vulnerability enables stored XSS: CVE-2026-18311 and CVE-2026-18312 through poisoned metadata, and CVE-2026-18320 through malicious SVG markup.

Solution

Unfortunately, the vendor could not be reached to coordinate this issue. Users should apply vendor updates as they become available (check Vendor Information section for updates) and keep Readwise Reader updated through the Google Play Store. As of publication, version 8.10.1 includes a patch that addresses the sanitizer-wildcard issue. Additionally, users should exercise caution when adding content from untrusted sources to their reading library and consider manually reviewing document metadata before saving articles to minimize exposure to malicious content.

Acknowledgements

Thanks to Zampier Zago (FUNFACTOR1) for reporting these vulnerabilities. This document was written by Alex Lewis.