Authorization bypass through predictable unsubscribe token in Popup Builder
Popup Builder generates newsletter unsubscribe tokens as an MD5 of the subscriber ID and e-mail address, a value an attacker can reproduce. An unauthenticated attacker who knows a subscriber’s e-mail address can brute-force the sequential subscriber ID to forge a valid unsubscribe link and remove that person from the site’s mailing list without their consent.
This vulnerability affects the following application versions:
- Popup Builder by Forward Looking 4.1.15
- Popup Builder by Forward Looking 4.2.0
- Popup Builder by Forward Looking 4.2.2
- Popup Builder by Forward Looking 4.2.3
- Popup Builder by Forward Looking 4.2.4
- Popup Builder by Forward Looking 4.2.5
- Popup Builder by Forward Looking 4.2.6
- Popup Builder by Forward Looking 4.2.7
- Popup Builder by Forward Looking 4.3.0
- Popup Builder by Forward Looking 4.3.2
- Popup Builder by Forward Looking 4.3.3
- Popup Builder by Forward Looking 4.3.4
- Popup Builder by Forward Looking 4.3.5
- Popup Builder by Forward Looking 4.3.6
- Popup Builder by Forward Looking 4.3.7
- Popup Builder by Forward Looking 4.3.8
- Popup Builder by Forward Looking 4.3.9
- Popup Builder by Forward Looking 4.4.0
- Popup Builder by Forward Looking 4.4.1
- Popup Builder by Forward Looking 4.4.2