# Open Source Event Calendar <= 1.2.0 - Authenticated (Author+) Missing Authorization to Arbitrary Post Modification via 'Edit this instance'

- **ID:** WPSEC-2026-2413
- **Plugin:** Open Source Event Calendar (`open-source-event-calendar`), https://wordpress.org/plugins/open-source-event-calendar/
- **Affected versions:** all versions before 1.2.1
- **Fixed in:** 1.2.1 (Update to 1.2.1 or later.)
- **Severity:** Medium 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N)
- **Weakness:** CWE-862
- **Usage among sites WPSec scans:** plugin Low, affected versions Low (as of 2026-11-03)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/open-source-event-calendar
- **Fix released:** 2026-11-02
- **Published:** 2026-11-03
- **URL:** https://wpsec.com/vuln/WPSEC-2026-2413/

## Description

The Open Source Event Calendar plugin for WordPress is vulnerable to unauthorized modification of data via the 'Edit this instance' occurrence handler (EventParent::admin_init_post() and EventEditing::create_duplicate_post()) in all versions up to, and including, 1.2.0. This is due to a missing capability check on the submitted post_ID, and to the handler passing every submitted post field (such as ID, post_type and meta_input) to wp_insert_post(). The handler runs on admin_action_editpost, before WordPress core's own edit checks. This makes it possible for authenticated attackers with author-level access and above (or the plugin's Event Contributor role) to change other users' events and their recurrence dates, and to overwrite arbitrary posts and add arbitrary post meta.

## References

- https://wpsec.com/vuln/WPSEC-2026-2413/
- https://plugins.svn.wordpress.org/open-source-event-calendar/tags/1.2.1/
- https://wordpress.org/plugins/open-source-event-calendar/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-2413/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to use, share and adapt, also commercially, if you credit WPSec and link to this advisory.