# CVE-2026-76579: LiteSpeed Cache <= 7.9 - Reflected Cross-Site Scripting via ESI 'esi' Parameter

> Unauthenticated attackers can inject arbitrary scripts via the ESI parameter in LiteSpeed Cache, executing code in victim browsers.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 19 Sep 2026
- **Updated:** 19 Sep 2026
- **Also known as:** GHSA-jf4h-cq6m-xhwf

## What is CVE-2026-76579?

CVE-2026-76579 is a medium-severity cross-site scripting vulnerability in litespeedtech LiteSpeed Cache, published on 19 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The LiteSpeed Cache plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'esi' parameter in all versions up to, and including, 7.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires that the attacker supply a validly signed 'esi' value in the GET query string while submitting a separate attacker-controlled 'esi' payload as a POST body field, relying on PHP's default $_REQUEST merge order to have the POST value take precedence at the point of execution.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-76579?


## How do I fix CVE-2026-76579?

No fix has been published for CVE-2026-76579 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-76579 being exploited?

There is no known exploitation of CVE-2026-76579 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76579 and fix it if it is affected.

What it is: CVE-2026-76579 is a medium-severity cross-site scripting vulnerability in litespeedtech LiteSpeed Cache, published on 19 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-76579 in the wild and no public exploit code.

Affected product: litespeedtech LiteSpeed Cache. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-76579/ (Markdown: https://insights.sbomify.com/CVE-2026-76579/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76579
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76579
- OSV: https://osv.dev/vulnerability/CVE-2026-76579

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-76579/
Summaries are generated and may contain mistakes; the official description above is the record.