# CVE-2026-27616: api XSS (High 7.3)

🐹

🐹 Go

Not in CISA KEV

HIGH severity

# CVE-2026-27616 — api

HIGH 

CVE-2026-27616 is a high-severity (CVSS 7.3) Cross-site Scripting (XSS) vulnerability in code.vikunja.io/api. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Vikunja Vulnerable to Stored Cross-Site Scripting (XSS) via Unsanitized SVG Attachment Upload Leading to Token Exposure

Also known as[GHSA-7jp5-298q-jg98](/vulnerability/GHSA-7jp5-298q-jg98)GO-2026-4553

Published

Feb 25, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

See advisory

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### Proof-of-concept exploit code exists

-   CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27616.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk

0.00%0.38%0.76%1.14%0.1%0.5%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

🐹`code.vikunja.io/api`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

## Description

**Details** The application allows users to upload SVG files as task attachments. SVG is an XML-based format that supports JavaScript execution through elements such as <script> tags or event handlers like onload.

The application does not sanitize SVG content before storing it. When the uploaded SVG file is accessed via its direct URL, it is rendered inline in the browser under the application's origin. As a result, embedded JavaScript executes in the context of the authenticated user.

Because the authentication token is stored in localStorage, it is accessible via JavaScript and can be retrieved by a malicious payload.

Key security issues identified:

_No server-side sanitization of SVG content. SVG attachments are rendered inline instead of being forced as a download. Embedded JavaScript within SVG files is allowed to execute. Authentication tokens stored in localStorage are accessible to client-side scripts._

**PoC**

_**Tested Environment**_

\[ \] Application version: 1.1.0 \[ \] Deployment type: Self-hosted

**Steps to Reproduce**

1.  Log in to an account.
2.  Go to Projects and Create a new task or open an existing task.
3.  Upload the following SVG file as an attachment:

```
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<svg
 onload="alert(localStorage.getItem('token'))"
 xmlns="http://www.w3.org/2000/svg">
</svg>

```

1.  After uploading ,save the Task and open the project , copy the direct URL of the attachment.
2.  Open the attachment URL in a new browser tab.
3.  The embedded JavaScript executes immediately and displays the authentication token stored in `localStorage`.

This confirms that arbitrary JavaScript embedded in an uploaded SVG file executes within the application's context.

**Impact**

This vulnerability is classified as **Stored Cross-Site Scripting (XSS).**

**Potential impact includes:**

Execution of arbitrary JavaScript in a victim’s browser. Exposure of authentication tokens. Potential account takeover. Ability to perform authenticated actions on behalf of the victim. Possible privilege escalation if higher-privileged users open the malicious attachment. Any authenticated user who accesses a malicious SVG attachment may be affected.

**Recommendations**

This vulnerability can be mitigated by implementing proper server-side sanitization of SVG uploads and preventing inline execution of uploaded files.

Specifically:

-   Sanitize all uploaded SVG files to remove <script> elements, event handlers (e.g., onload), and other executable content.
-   Serve attachments with Content-Disposition: attachment to prevent inline rendering.
-   Implement a strict Content Security Policy (CSP) to block script execution within uploaded files.
-   Store authentication tokens in HttpOnly, Secure cookies instead of localStorage to prevent JavaScript access.
-   Applying these controls will prevent stored XSS via SVG uploads and significantly reduce the risk of token exposure and account takeover.

**Attachment** [Stored XSS Proof of concept.pdf](https://github.com/user-attachments/files/25414870/Stored.XSS.Proof.of.concept.pdf)

A fix is available at [https://github.com/go-vikunja/vikunja/releases/tag/v2.0.0](https://github.com/go-vikunja/vikunja/releases/tag/v2.0.0).

## Affected Packages

1 total

Ecosystem

Package

Vulnerable range

Fix

🐹Go

`code.vikunja.io/api` 

all versions

No fix

## Affected Products

1 product · 1 configurations

Application

`vikunja`vikunja

< 2.0.0

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for code.vikunja.io/api, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Remediation status
    
    The records we use list no patched version of code.vikunja.io/api for CVE-2026-27616. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
    
3.  ### Mitigate without a patch
    
    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
    

## Frequently Asked Questions

\*\*Details\*\* The application allows users to upload SVG files as task attachments. SVG is an XML-based format that supports JavaScript execution through elements such as <script> tags or event handlers like onload. The application does not sanitize SVG content before storing it. When the uploaded SVG file is accessed via its direct URL, it is rendered inline in the browser under the application's origin. As a result, embedded JavaScript executes in the context of the authenticated user. Because the authentication token is stored in localStorage, it is accessible via JavaScript and can be retr

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