My Calendar <= 3.8.3 — Authenticated (Contributor+) Stored Cross-Site Scripting via 'fallback' Shortcode Attribute
CVE-2026-77186Published · Updated Action summary
Affected: ≤3.8.3Update to 3.8.4 or newer
All remediation steps- Severity
- Medium6.4
- CVSS
- 6.4CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:NWhat does this vector mean?
AV:NAttack vector- Network
AC:LAttack complexity- Low
PR:LPrivileges required- Low
UI:NUser interaction- None
S:CScope- Changed
C:LConfidentiality- Low
I:LIntegrity- Low
A:NAvailability- None
- Weakness
- CWE-79 Cross-Site Scripting
- Required access
- Unknown
- Exploit prediction (EPSS)
- 0.4% chance in 30 days29th percentile
- CISA KEV
- Not listed
On this page8
Am I affected?
My Calendar – Accessible Event Manager my-calendar
- Affected≤ 3.8.3
- Patched in3.8.4
Update to 3.8.4 or newer.
You are affected if you run ≤ 3.8.3. Version 3.8.4 and later are not affected by this issue.
- Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under My Calendar – Accessible Event Manager.
- No admin access? Run a passive check of your site. It reads public files only.
What to do
- Update to version 3.8.4, or a newer patched version
- Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
- Watch My Calendar – Accessible Event Manager to get an email when the next vulnerability is published.
Advisory
Source description from Wordfence Intelligence, credited to Wordfence PRISM.
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.
Exploits & references
Proof-of-concept & detection
No public proof-of-concept or detection template is known for this vulnerability.
Advisories & patches
- Advisorywordfence.com
Related CVEs
More in My Calendar – Accessible Event Manager
All 24| Severity | Vulnerability | CVE | Published |
|---|---|---|---|
| Medium6.5 | 3.8.11 - Unauthenticated Arbitrary Shortcode Execution 3.8.8 – <3.8.11Update to 3.8.11 | CVE-2026-119714 | |
| Critical9.8 | Unauthenticated Privilege Escalation to 'mcs' Parameter via Reflected Shortcode Injection into 'above' Attribute ≤3.8.7Update to 3.4.25 or 3.5.22 or 3.6.18 or 3.7.18 or 3.8.8 | CVE-2026-104798 | |
| Medium6.4 | Authenticated (Contributor+) Stored Cross-Site Scripting via 'before' and 'after' Shortcode Attributes ≤3.8.3Update to 3.8.4 | CVE-2026-77187 | |
| High7.5 | Unauthenticated SQL Injection via 'mc_auth' and 'mc_host' Parameters ≤3.7.8Update to 3.7.9 | CVE-2026-6854 | |
| Medium5.3 | Insecure Direct Object Reference to Unauthenticated Sensitive Information Disclosure via 'vcal' Parameter ≤3.7.14Update to 3.7.15 | CVE-2026-11896 |
- Medium6.53.8.11 - Unauthenticated Arbitrary Shortcode Execution
3.8.8 – <3.8.11Update to 3.8.11
- Critical9.8Unauthenticated Privilege Escalation to 'mcs' Parameter via Reflected Shortcode Injection into 'above' Attribute
≤3.8.7Update to 3.4.25 or 3.5.22 or 3.6.18 or 3.7.18 or 3.8.8
- Medium6.4Authenticated (Contributor+) Stored Cross-Site Scripting via 'before' and 'after' Shortcode Attributes
≤3.8.3Update to 3.8.4
- High7.5Unauthenticated SQL Injection via 'mc_auth' and 'mc_host' Parameters
≤3.7.8Update to 3.7.9
- Medium5.3Insecure Direct Object Reference to Unauthenticated Sensitive Information Disclosure via 'vcal' Parameter
≤3.7.14Update to 3.7.15
Same weakness (Cross-Site Scripting)
All Cross-Site Scripting| Severity | Vulnerability | CVE | Published |
|---|---|---|---|
| High7.2 | Unauthenticated Stored Cross-Site Scripting via Comment User-Agent Header | CVE-2026-120688 | |
| Critical9.8 | Unauthenticated Arbitrary File Upload via File Upload via Public Form Submission | CVE-2026-125055 | |
| Critical9.8 | Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter | CVE-2026-119077 | |
| Medium5.3 | Unauthenticated Sensitive Information Exposure in 'search' Parameter | CVE-2026-121518 |
- High7.2Unauthenticated Stored Cross-Site Scripting via Comment User-Agent Header
EZ SQL Reports Shortcode Widget and DB Backup
≤5.25.25Update to 5.26.45
- Critical9.8Unauthenticated Arbitrary File Upload via File Upload via Public Form Submission
Chatterbug Forms – Fast, Flexible WordPress Form Builder
≤1.0.2Update to 1.1
- Critical9.8Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter
ELEX WordPress HelpDesk & Customer Ticketing System
≤3.3.9Update to 3.4.0
- Medium5.3Unauthenticated Sensitive Information Exposure in 'search' Parameter
Customer Reviews for WooCommerce
≤5.127.0Update to 5.128.0
Timeline
CVE published
Severity medium, CVSS 6.4
Record last updated
Sources & licenses
Wordfence record- Vulnerability data
- Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
- CVE® identifiers
- Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
- CVSS / CWE
- National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
- EPSS
- Exploit Prediction Scoring System by FIRST.org.
- VulnCrest content
- Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.