# CVE-2026-77186: My Calendar <= 3.8.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'fallback' Shortcode Attribute

> Authenticated contributors can inject arbitrary scripts via hex-encoded shortcode attributes, leading to stored XSS execution for other users.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-588q-hr78-m65w

## What is CVE-2026-77186?

CVE-2026-77186 is a medium-severity cross-site scripting vulnerability in joedolson My Calendar – Accessible Event Manager, published on 9 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'fallback' Shortcode Attribute in all versions up to, and including, 3.8.3 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The bypass relies on hex-encoded shortcode attribute payloads (e.g. \x3cscript\x3e), which wp_kses_post cannot strip on save because they appear as literal backslash sequences rather than real HTML tags; WordPress core's shortcode_parse_atts() then calls stripcslashes() at render time, decoding the escapes into real angle brackets before they reach the unescaped sink.

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

## Which versions are affected by CVE-2026-77186?


## How do I fix CVE-2026-77186?

No fix has been published for CVE-2026-77186 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77186 being exploited?

There is no known exploitation of CVE-2026-77186 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77186 and fix it if it is affected.

What it is: CVE-2026-77186 is a medium-severity cross-site scripting vulnerability in joedolson My Calendar – Accessible Event Manager, published on 9 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77186 in the wild and no public exploit code.

Affected product: joedolson My Calendar – Accessible Event Manager. 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-2026-77186/ (Markdown: https://insights.sbomify.com/CVE-2026-77186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77186
- OSV: https://osv.dev/vulnerability/CVE-2026-77186

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-77186/
Summaries are generated and may contain mistakes; the official description above is the record.