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💎 RubyGems
Not in CISA KEV
MEDIUM severity

CVE-2021-35440 — smashing

MEDIUMFix: Smashing/smashing#186

CVE-2021-35440 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in smashing. A fix is available for smashing — see the affected versions and patch details below.

Smashing Cross-site Scripting vulnerability

Also known asGHSA-254j-mmc5-qhpx
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.0%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk
0.00%0.50%1.00%1.49%0.3%1.0%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
💎smashing

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS). A URL for a widget can be crafted and used to execute JavaScript on the victim's computer. The JavaScript code can then steal data available in the session/cookies depending on the user environment (e.g. if re-using internal URL's for deploying, or cookies that are very permissive) private information may be retrieved by the attacker.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemssmashingall versions1.3.5bundle update smashing --conservative

Affected Products

1 product · 1 configurations
Application
smashingsmashing_project
1 version
1.3.4

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for smashing, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update smashing to 1.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-35440 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS). A URL for a widget can be crafted and used to execute JavaScript on the victim's computer. The JavaScript code can then steal data available in the session/cookies depending on the user environment (e.g. if re-using internal URL's for deploying, or cookies that are very permissive) private information may be retrieved by the attacker.
O3 Security · Impact-Aware SCA

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CVE-2021-35440: smashing XSS — Fixed in 1.3.5