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MEDIUM severity

CVE-2024-55878 — simplexlsx

MEDIUMFix: shuchkin/simplexlsx@cb4e716

CVE-2024-55878 is a medium-severity (CVSS 6.8) Cross-site Scripting (XSS) vulnerability in shuchkin/simplexlsx. A fix is available for shuchkin/simplexlsx — see the affected versions and patch details below.

Cross-site Scripting vulnerability in SimpleXLSXEx::readXfs and SimpeXLSX::toHTMLEx

Also known asGHSA-x6mh-rjwm-8ph7
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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-2024-55878.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk
0.00%0.32%0.64%0.96%0.2%0.5%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
🐘shuchkin/simplexlsx

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

Description

SimpleXLSX is software for parsing and retrieving data from Excel XLSx files. Starting in version 1.0.12 and prior to version 1.1.12, when calling the extended toHTMLEx method, it is possible to execute arbitrary JavaScript code. Version 1.1.12 fixes the issue. As a workaround, don't use direct publication via toHTMLEx.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistshuchkin/simplexlsx≥ 1.0.12&&< 1.1.121.1.12composer require shuchkin/simplexlsx:^1.1.12

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update shuchkin/simplexlsx to 1.1.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-55878 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

SimpleXLSX is software for parsing and retrieving data from Excel XLSx files. Starting in version 1.0.12 and prior to version 1.1.12, when calling the extended toHTMLEx method, it is possible to execute arbitrary JavaScript code. Version 1.1.12 fixes the issue. As a workaround, don't use direct publication via toHTMLEx.
O3 Security · Impact-Aware SCA

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CVE-2024-55878: simplexlsx — Fixed in 1.1.12