# CVE-2026-57958: Mixpost 2.6.0 - Reflected XSS via OAuth Callback Error Parameter

> Unauthenticated attackers can execute arbitrary JavaScript in authenticated users' browsers via malicious OAuth callback URLs, leading to session hijacking.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA: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:** 29 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** GHSA-x4g3-x4c9-rjf8

## What is CVE-2026-57958?

CVE-2026-57958 is a medium-severity cross-site scripting vulnerability in inovector mixpost, published on 29 Jun 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

Mixpost through 2.6.0 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to execute arbitrary JavaScript in authenticated users' browsers by crafting malicious OAuth callback URLs with unsanitized error query parameters. Attackers can exploit the OAuth callback controller's failure to sanitize error parameters before rendering them through Laravel flash messages via the Vue v-html directive to hijack authenticated user sessions or perform unauthorized actions.

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

## Which versions are affected by CVE-2026-57958?


## How do I fix CVE-2026-57958?

No fix has been published for CVE-2026-57958 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57958 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57958 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57958 and fix it if it is affected.

What it is: CVE-2026-57958 is a medium-severity cross-site scripting vulnerability in inovector mixpost, published on 29 Jun 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57958 exists.

Affected product: inovector mixpost. 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-2026-57958/ (Markdown: https://insights.sbomify.com/CVE-2026-57958/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57958
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57958
- OSV: https://osv.dev/vulnerability/CVE-2026-57958

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57958/
Summaries are generated and may contain mistakes; the official description above is the record.