CVE-2026-48527
HIGHCVE-2026-48527 is a high-severity (CVSS 8.7) Cross-site Scripting (XSS) vulnerability in @haxtheweb/haxcms-nodejs. O3 Security confirms whether CVE-2026-48527 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
HaxCMS has a stored Cross-Site Scripting (XSS) bypass in its saveNode endpoint
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-48527.
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-2026-48527 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 0 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.
@haxtheweb/haxcms-nodejsnpmDescription
Summary
HaxCMS is affected by a stored cross-site scripting (XSS) vulnerability in the /system/api/saveNode endpoint. An authenticated user with a permission to edit pages can bypass the HTML sanitizer by injecting an event handler attribute without whitespace before the attribute name.
For example, the sanitizer misses:
<a href="#"onclick="alert('kn1ph')">click me</a>
The important bypass is:
href="#"onclick=
The payload is stored in the generated page files and executes when a user clicks the injected link.
Details
The issue is caused by regex-based HTML sanitization that expects whitespace before event handler attributes. Because the sanitizer expects a pattern like:
href="#" onclick="..."
It fails to remove an event handler when it is written without whitespace:
href="#"onclick="..."
Browsers still parse onclick as a valid event handler attribute, so the JavaScript executes when the element is clicked.
Affected endpoint:
POST /system/api/saveNode?site_token=[VALID_SITE_TOKEN]
Affected parameter:
node.body
PoC
-
Log in to HaxCMS and edit any existing page.
-
Capture the page save request in Burp Suite:
POST /system/api/saveNode?site_token=[VALID_SITE_TOKEN]
- In the JSON request body, modify only the
node.bodyvalue.
Change:
"body":"...existing page content...\n"
To:
"body":"...existing page content...\n<a href=\"#\"onclick=\"alert('kn1ph')\">click me</a>\n"
-
Forward the request.
-
Open the edited page and click
click me.
Result:
The JavaScript will execute and the alert will pop up.
It was confirmed that the payload is stored in the generated page files, including index.html.
Impact
An authenticated user with permissions to edit the page can inject stored JavaScript into the page content. If a privileged user interacts with the injected element while authenticated, the attacker controlled JavaScript will execute in that user’s browser.
Based on local testing, the XSS can access browser-exposed HaxCMS data such as localStorage.jwt and window.appSettings, including API paths and tokens available to the authenticated user.
This may allow an attacker to perform actions as the victim within the limits of the exposed tokens and the victim’s permissions and possibly chain more vulnerabilities.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @haxtheweb/haxcms-nodejs | all versions | 26.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @haxtheweb/haxcms-nodejs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @haxtheweb/haxcms-nodejs to 26.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48527 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 pinpoints whether CVE-2026-48527 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-48527. 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-2026-48527 in your dependencies?
O3 detects CVE-2026-48527 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.