CVE-2023-37259 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in matrix-react-sdk. A fix is available for matrix-react-sdk — see the affected versions and patch details below.
Cross site scripting in Export Chat feature
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-37259.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-37259 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
matrix-react-sdknpmDescription
matrix-react-sdk is a react-based SDK for inserting a Matrix chat/voip client into a web page. The Export Chat feature includes certain attacker-controlled elements in the generated document without sufficient escaping, leading to stored Cross site scripting (XSS). Since the Export Chat feature generates a separate document, an attacker can only inject code run from the null origin, restricting the impact. However, the attacker can still potentially use the XSS to leak message contents. A malicious homeserver is a potential attacker since the affected inputs are controllable server-side. This issue has been addressed in commit 22fcd34c60 which is included in release version 3.76.0. Users are advised to upgrade. The only known workaround for this issue is to disable or to not use the Export Chat feature.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | matrix-react-sdk | ≥ 3.32.0&&< 3.76.0 | 3.76.0npm install matrix-react-sdk@3.76.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-react-sdk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update matrix-react-sdk to 3.76.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-37259 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-37259 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-37259. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-37259 in your dependencies?
O3 Security finds CVE-2023-37259 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.