Decidim: HTML content blocks allow stored script execution

published 2026-07-13 3 mo ago modified 2026-09-08 2 mo ago also EUVD-2026-54251 , GHSA-533c-2vh9-4r86

cvss: 4.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits: 0; none known

Decidim is a participatory democracy framework. Prior to 0.30.9, from 0.31.0 before 0.31.5, and in 0.32.0.rc1 before 0.32.0.rc2, an administrator with landing-page editing privileges can store arbitrary HTML and JavaScript in an HTML content block, which Decidim::ContentBlocks::HtmlCell#html_content renders without sanitization, causing the script to execute in visitors' browsers. This issue is fixed in versions 0.30.9, 0.31.5, and 0.32.0.rc2.

Patch / fix

fixed in 2 links 1

rubygems decidim-core 0.30.9, 0.31.5, 0.32.0
decidim decidim 0.30.9, 0.31.5, 0.32.0

github.com/decidim/decidim#16451 pull request

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 3 mo ago (2026-08-07)

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
GitHub	3.1	4.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
rubygems	decidim-core	<0.30.9 >=0.31.0.rc1, <0.31.5 >=0.32.0.rc1, <0.32.0	0.30.9 0.31.5 0.32.0

Affected products

decidim decidim

Classification

Weakness

CWE-94 Improper Control of Generation of Code

References

Sources

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary