fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes
Summary
When an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML.
Detail
Malicious Input
{
a: {
"@_attr": '" onClick="alert(1)'
}
}Output
<a attr="" onClick="alert(1)"></a>Workarounds
If you're not ignoring attributes then keep processEntities flag true.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | fast-xml-builder | < 1.1.7 | 1.1.7 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-611, CWE-91- Platform
- npm
- Package
fast-xml-builder- Disclosed
- 08.05.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-5wm8-gmm8-39j9 - CC BY 4.0
Vulnerability history: fast-xml-builder
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 05.2026 05.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 1
Disclosures per year
- 2026: 2
-
fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes this entry
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