Cross-site scripting via raw async helper substitution
Published Aug 25, 2026 · Updated Aug 25, 2026
Cross-site scripting in PillarJS hbs 2.1.0 through 4.2.1 allows remote attackers to inject script through async helper output. The registerAsyncHelper render flow escapes an opaque placeholder, then replaces it with the callback's raw return value after rendering. Exploitation requires attacker-controlled helper data and a victim browser to load the rendered page, enabling script execution in that page context.
Summary
What happened
Cross-site scripting in PillarJS hbs 2.1.0 through 4.2.1 allows remote attackers to inject script through async helper output. The registerAsyncHelper render flow escapes an opaque placeholder, then replaces it with the callback's raw return value after rendering. Exploitation requires attacker-controlled helper data and a victim browser to load the rendered page, enabling script execution in that page context.
The record
- CVE
- CVE-2026-16231
- Published
- Aug 25, 2026
- Updated
- Aug 25, 2026
- Vendor
- PillarJS
- Product
- hbs
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 25, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.1.0 <4.3.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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