The Online Scheduling and Appointment Booking System WordPress plugin before 28.3 does not verify that appointment and payment records requested through its staff-role AJAX actions belong to the requesting staff member, allowing authenticated attackers with a staff-level account to view, modify and delete other staff members' appointments and payments, including the associated customer's personal information.

The Online Scheduling and Appointment Booking System WordPress plugin before 28.3 does not prevent deserialization of untrusted input and does not correctly restrict a privileged maintenance feature to administrators, allowing users granted a custom booking-management capability, which an administrator must explicitly assign, to inject arbitrary PHP objects, overwrite privileged site options, and read stored integration secrets.

The Bookly WordPress plugin before 28.3 does not properly verify a customer's identity before updating their stored details, allowing unauthenticated attackers who know a customer's primary identifier to overwrite that customer's stored personal information such as name, email and address.

The Online Scheduling and Appointment Booking System – Bookly plugin for WordPress is vulnerable to Authorization Bypass via PHP Type Juggling in all versions up to, and including, 28.2. This is due to the postValidateCustomer() function using a loose PHP inequality operator (!=) to compare the session-stored one-time verification code against the attacker-supplied verificationcode parameter — a flaw that is further exposed by the booking AJAX controller registering all its methods as wpajaxnopriv handlers and unconditionally overriding csrfTokenValid() to return true, leaving the endpoint both unauthenticated and CSRF-unprotected. This makes it possible for unauthenticated attackers to bypass the phone/email ownership verification step and overwrite the name, email, phone, and address fields of any arbitrary existing Bookly customer record, redirecting that customer's booking notifications to attacker-controlled contact details. The bypass is achievable because the jsondata input channel decodes input via jsondecode(), which preserves real PHP types and causes the wpkses filter to leave non-string values such as the JSON boolean true untouched; submitting true as the verificationcode satisfies the loose comparison against the session's non-zero integer code (generated by mtrand(100000, 999999)), causing true != <non-zero int> to evaluate as false and the guard to be bypassed.

Unauthenticated Sensitive Data Exposure in Bookly <= 27.4 versions.

The Online Scheduling and Appointment Booking System – Bookly plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'bookly-customer-full-name' cookie in versions up to, and including, 27.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Exploitation requires 'Remember personal information in cookies' setting to be enabled (disabled by default).

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Bookly Bookly bookly-responsive-appointment-booking-tool allows Reflected XSS.This issue affects Bookly: from n/a through <= 26.7.