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GHSA-6738-r8g5-qwp3

MediumCVSS 5.3 / 10
Published Jan 15, 2026·Last modified Feb 3, 2026
Affected Components(0)

No affected components available

Description

Summary

An XSS vulnerability exists in Svelte 5.46.0-2 resulting from improper escaping of hydratable keys. If these keys incorporate untrusted user input, arbitrary JavaScript can be injected into server-rendered HTML.

Details

When using the hydratable function, the first argument is used as a key to uniquely identify the data, such that the value is not regenerated in the browser.

This key is embedded into a <script> block in the server-rendered <head> without escaping unsafe characters. A malicious key can break out of the script context and inject arbitrary JavaScript into the HTML response.

Impact

This is a cross-site scripting vulnerability affecting applications that have the experimental.async flag enabled and use hydratable with keys incorporating untrusted user input.

  • Impact: Arbitrary JS execution in the client’s browser.
  • Exploitability: Remote, single-request if key is attacker-controlled.
  • Typical Outcomes:
    • Session/token theft
    • DOM defacement
    • CSRF bypass via injected JS
    • Account takeover depending on cookie/session strategy

Affected applications should upgrade to a patched version immediately.

Risk Scores
Base Score
5.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence
1.3

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.30%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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