Malicious website can execute commands on the local system through XSS in the OpenCode web UI

published 2026-01-12 9 mo ago modified 2026-06-17 4 mo ago also GHSA-c83v-7274-4vgp , EUVD-2026-2091

cvss: 6.1; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits: 0; none known

OpenCode is an open source AI coding agent. The markdown renderer used for LLM responses will insert arbitrary HTML into the DOM. There is no sanitization with DOMPurify or even a CSP on the web interface to prevent JavaScript execution via HTML injection. This means controlling the LLM response for a chat session gets JavaScript execution on the http://localhost:4096 origin. This vulnerability is fixed in 1.1.10.

Patch / fix

fixed in 2

npm opencode-ai 1.1.10
anoma opencode 1.1.10

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: total
Assessed: 9 mo ago (2026-01-13)

Exploit prediction

0.91% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/anomalyco/opencode/security/advisories/GHSA-c83v-7274-4vgp referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	9.4	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CNA	4.0	9.4	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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
NVD	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	opencode-ai	<1.1.10	1.1.10

Affected products

anomalyco opencode

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

github.com /anomalyco/opencode/security/advisories/GHSA-c83v-7274-4vgp
exploit, web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-22813
advisory
github.com /anomalyco/opencode
package

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.

Summary