they are usually mentioned in the install file
eg:
ftp://download1.sw-soft.com/Plesk/Plesk7.5/RedHatEL4.0/psa-7.5.4-rhel4.build75051017.14.i586.txt
What's new in Plesk v.7.5.4 build 75051017.14
==============================================
[-] Several PMM, API-RPC, CU bugs are fixed
[-] mchk bug with segmentation fault is fixed
[+] Sitebuilder 2.1.1 is added
[+] SBM 2.0 is added
What's new in Plesk v.7.5.4 build 75050928.18
==============================================
[-] Dr. Web starting causes qmail-queue to loose suid bit
[-] Sheduled Backups reset last timestamp
[-] Proftpd problem with group owner during file uploading
[-] Spam mail isn't deleted/marked
[-] Spamassassin corrupted by Watchdog
[-] Value for checkbox 'WWW-prefix' missed if domain administrator changes properties of the account
[-] Wrong permissions for /var/qmail/bin/qmail-queue after start/stop of Drweb
[-] Plesk does not recognize main IP
[*] Germany LP for watchdog is updated
[-] phpBB issue is fixed
What's new in Plesk v.7.5.4 build 75050915.19
==============================================
[-] 1. Fixed bugs in PMM with RaQ2 migration
[-] 2. Fixed bug in domain.sh CU with DNS zone management
[-] 3. Fixed bug in PMM with mail aliases migration
[-] 4. Fixed bug in cs-gs module with upgrade from 1.2.2 to 1.2.3
[-] 5. Fixed bug in HSPc: Plesk can't connect with MYSQL on VE created through HSPc
[+] 6. New plesk's component autoupdater is added