An issue was discovered in BACKCLICK Professional 5.9.63. Due to the use of consecutive IDs in verification links, the newsletter sign-up functionality is vulnerable to the enumeration of subscribers' e-mail addresses. Furthermore, it is possible to subscribe and verify other persons' e-mail addresses to newsletters without their consent.
An issue was discovered in BACKCLICK Professional 5.9.63. Due to the use of consecutive IDs in verification links, the newsletter sign-up functionality is vulnerable to the enumeration of subscribers' e-mail addresses. Furthermore, it is possible to subscribe and verify other persons' e-mail addresses to newsletters without their consent.