CVE-2020-25828 — mediawiki/core
MEDIUMCVE-2020-25828 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in mediawiki/core. A fix is available for mediawiki/core — see the affected versions and patch details below.
MediaWiki Cross-site Scripting (XSS) vulnerability
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-25828 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
mediawiki/core🐘mediawiki/core🐘mediawiki/coreReal-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
An issue was discovered in MediaWiki before 1.31.10 and 1.32.x through 1.34.x before 1.34.4. The non-jqueryMsg version of mw.message().parse() doesn't escape HTML. This affects both message contents (which are generally safe) and the parameters (which can be based on user input). (When jqueryMsg is loaded, it correctly accepts only whitelisted tags in message contents, and escapes all parameters. Situations with an unloaded jqueryMsg are rare in practice, but can for example occur for Special:SpecialPages on a wiki with no extensions installed.)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | mediawiki/core | ≥ 1.31.0&&< 1.31.9 | 1.31.9composer require mediawiki/core:^1.31.9 |
| 🐘Packagist | mediawiki/core | ≥ 1.32.0&&< 1.34.3 | 1.34.3composer require mediawiki/core:^1.34.3 |
| 🐘Packagist | mediawiki/core | ≥ 1.35.0-rc.0&&< 1.35.0 | 1.35.0composer require mediawiki/core:^1.35.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mediawiki/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mediawiki/core to 1.31.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-25828 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2020-25828 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-25828. 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-2020-25828 in your dependencies?
O3 Security finds CVE-2020-25828 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.