I9300 4.3 Unlock Done.[Reference]
1st step root your I9300 version 4.3 using this tutorials link
2nd Connect your I9300 to PC then open Octoplus version 1.4.8
3rd Click Read then Click Unlock
LOGS
Welcome to Octoplus/Octopus Box Samsung software version 1.4.8
-----------------------------------------------------------------------------------
To connect GT-I9300 phone you have to perform the following steps:
1. Disconnect USB cable from phone.
2. Go to Menu->Settings->Developer options.
3. Turn on "USB Debugging" option.
4. When message is appear press "Yes".
5. Connect usb cable to phone.
6. Go to dial window.
7. Enter *#9090# number.
8. Set speed to 115200.
9. Reboot phone.
10. Press "Read Info" in software.
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM10
Selected model: GT-I9300
Reading info, please wait...
Detected phone model: GT-I9300
Firmware compiled date: Thu Nov 28 21:07:41 KST 2013
PDA version: I9300XXUGMK6
CSC version: I9300OLBGML1
SW version: I9300DXUGMK1
Phone IMEI: 35609605XXXXXXXX
Phone SN: RF1D2XXXXX
Android version: 4.3 (JSS15J)
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM10
Selected model: GT-I9300
Detected phone model: GT-I9300
Firmware compiled date: Thu Nov 28 21:07:41 KST 2013
PDA version: I9300XXUGMK6
CSC version: I9300OLBGML1
SW version: I9300DXUGMK1
Phone IMEI: 35609605XXXXXXXX
Phone SN: RF1D2XXXXXX
Android version: 4.3 (JSS15J)
Checking Root:
Phone is Rooted.
Reading security backup, please wait...
Backup saved as C:\Program Files\Octoplus\Octoplus_Samsung
\BACKUP\Security-GT-I9300-Unknown11-02-2014_12-33-48-.asec file
Cheking security type...
New security type is detected
Executing exploit...
Exploit has been executed successfully
Unlocking phone. This can take some time. Please wait...
Phone will restart now
Phone is successfully unlocked
2nd Connect your I9300 to PC then open Octoplus version 1.4.8
3rd Click Read then Click Unlock
LOGS
Welcome to Octoplus/Octopus Box Samsung software version 1.4.8
-----------------------------------------------------------------------------------
To connect GT-I9300 phone you have to perform the following steps:
1. Disconnect USB cable from phone.
2. Go to Menu->Settings->Developer options.
3. Turn on "USB Debugging" option.
4. When message is appear press "Yes".
5. Connect usb cable to phone.
6. Go to dial window.
7. Enter *#9090# number.
8. Set speed to 115200.
9. Reboot phone.
10. Press "Read Info" in software.
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM10
Selected model: GT-I9300
Reading info, please wait...
Detected phone model: GT-I9300
Firmware compiled date: Thu Nov 28 21:07:41 KST 2013
PDA version: I9300XXUGMK6
CSC version: I9300OLBGML1
SW version: I9300DXUGMK1
Phone IMEI: 35609605XXXXXXXX
Phone SN: RF1D2XXXXX
Android version: 4.3 (JSS15J)
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM10
Selected model: GT-I9300
Detected phone model: GT-I9300
Firmware compiled date: Thu Nov 28 21:07:41 KST 2013
PDA version: I9300XXUGMK6
CSC version: I9300OLBGML1
SW version: I9300DXUGMK1
Phone IMEI: 35609605XXXXXXXX
Phone SN: RF1D2XXXXXX
Android version: 4.3 (JSS15J)
Checking Root:
Phone is Rooted.
Reading security backup, please wait...
Backup saved as C:\Program Files\Octoplus\Octoplus_Samsung
\BACKUP\Security-GT-I9300-Unknown11-02-2014_12-33-48-.asec file
Cheking security type...
New security type is detected
Executing exploit...
Exploit has been executed successfully
Unlocking phone. This can take some time. Please wait...
Phone will restart now
Phone is successfully unlocked