CVE-2024-55878
MEDIUMCVE-2024-55878 is a medium-severity (CVSS 6.8) Cross-site Scripting (XSS) vulnerability in shuchkin/simplexlsx. O3 Security confirms whether CVE-2024-55878 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-site Scripting vulnerability in SimpleXLSXEx::readXfs and SimpeXLSX::toHTMLEx
Blast Radius
shuchkin/simplexlsxReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | shuchkin/simplexlsx | ≥ 1.0.12&&< 1.1.12 | 1.1.12 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shuchkin/simplexlsx. 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 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.
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-2024-55878 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-2024-55878. 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-2024-55878 in your dependencies?
O3 detects CVE-2024-55878 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.