vulnerability / NVI-00005601 / Revision 2
Unauthenticated Information Disclosure (IDOR) via Multisite switch_to_blog in My Calendar
OSV carries this publisher advisory for joedolson/my-calendar. This is an aggregated source copy; consult the original publisher and compare update dates.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
0.932%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.60692. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
joedolson/my-calendar
source listedECOSYSTEM: introduced 0; fixed 3.7.7
### Summary An unauthenticated Insecure Direct Object Reference (IDOR) and Denial of Service (DoS) vulnerability in the My Calendar plugin allows any unauthenticated user to extract calendar events (including private or hidden ones) from any sub-site on a WordPress Multisite network. On standard Single Site WordPress installations, this same endpoint crashes the PHP worker thread, creating an unauthenticated Denial of Service (DoS) vector. ### Details The vulnerability stems from the `mc_ajax_mcjs_action AJAX` function, which handles the `mcjs_action` endpoint. This endpoint is explicitly registered for unauthenticated users: ```php <?php // In my-calendar-ajax.php add_action( 'wp_ajax_nopriv_mcjs_action', 'mc_ajax_mcjs_action' ); ``` When the behavior parameter is set to loadupcoming, the plugin accepts an args parameter from the $_REQUEST array. Instead of validating specific expected arguments, the plugin unsafely passes the entire string into PHP's parse_str() function: ```php <?php $request = isset( $_REQUEST['args'] ) ? wp_unslash( sanitize_text_field( $_REQUEST['args'] ) ) : array(); $request = str_replace( '|', '&', $request ); $request = parse_str( $request, $args ); /
03 / Response
What to do next
- vendor patch
The original advisory lists fixed boundaries 3.7.7 for joedolson/my-calendar. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-2mvx-f5qm-v2ch ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-40308 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.