TemplateSandbox can be abused for XSS by asking another user to preview a page with a certain sandbox prefix

published 2026-09-25 44 d ago modified 2026-09-28 41 d ago also EUVD-2026-87359

cvss: 4.8; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits: 0; none known

Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Wikimedia Foundation Mediawiki - TemplateSandbox Extension allows Cross-Site Scripting (XSS).

This issue affects Mediawiki - TemplateSandbox Extension: from * before 1.46.1, 1.45.5, 1.43.10.

Patch / fix

fixed in 1

Wikimedia Foundation Mediawiki - TemplateSandbox Extension 1.46.1, 1.45.5, 1.43.10

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-100376 updated 2026-09-29 cvss 5.4

mediawiki: mediawiki: Cross-Site Scripting in TemplateSandbox via crafted preview prefix

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 43 d ago (2026-09-26)

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	4.8	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L
CNA	4.0	4.8	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

Wikimedia Foundation Mediawiki - TemplateSandbox Extension

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

CVE List CVE-2026-100376
NVD CVE-2026-100376

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary