"Newsletter subscriber management" (fp_newsletter) TYPO3 extension leaks subscriber data

An issue was discovered in the fpnewsletter aka Newsletter subscriber management extension before 1.1.1, 1.2.0, 2.x before 2.1.2, 2.2.1 through 2.4.0, and 3.x before 3.2.6 for TYPO3. Data about subscribers may be obtained via unsubscribeAction operations...