CVE-2026-18311 Readwise CVE debrief

Who should care

Defenders responsible for securing Android devices and Readwise Reader for Android installations should assess exposure and prioritize verification and updates to prevent potential XSS attacks.

Why it matters

CVE-2026-18311 is a cross-site scripting vulnerability in Readwise Reader for Android that allows attacker-controlled fields to be inserted into a WebView via innerHTML, enabling stored XSS. Defenders should prioritize verification and updates to prevent potential XSS attacks.

• Defenders must verify and update Readwise Reader for Android to prevent potential XSS attacks
• Security teams should monitor for suspicious activity related to the vulnerability
• Android device administrators should ensure that Readwise Reader for Android is properly configured and secured

Technical summary

The vulnerability is caused by missing HTML sanitization in the processing of imported document metadata in Readwise Reader for Android. This allows attacker-controlled fields, such as the author meta tag, to be inserted into a WebView via innerHTML, enabling stored XSS that executes on synced devices when the malicious document is opened. The vulnerability allows for stored XSS attacks, which can be executed when a malicious document is opened on synced devices. Defenders should prioritize verifying and updating Readwise Reader for Android to prevent potential XSS attacks.

Defensive priority

Defenders should prioritize verifying and updating Readwise Reader for Android to prevent potential XSS attacks.

Recommended defensive actions

• Verify and update Readwise Reader for Android to the latest version
• Implement additional security measures to prevent XSS attacks
• Monitor for suspicious activity related to the vulnerability
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is described in the CVE and NVD records, with a CVSS score of 6.1 and severity of MEDIUM. The CVE record was published on 2026-09-25T17:17:07.657Z and has not been modified since then. Evidence is limited to public CVE and NVD records. Defenders should verify the vulnerability and update Readwise Reader for Android to the latest version. The vulnerability is caused by missing HTML sanitization in the processing of imported document metadata.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.