This is the trickiest part. Cisco does not allow direct public downloads of most phone firmware due to licensing restrictions. Here is the hierarchy of legal sources:
Let’s face it—nobody is paying for a SmartNet contract to support a $20 phone from 2009. Here is where the community helps. Cisco Ip Phone 7965 Firmware Download
Here is where the "solid review" turns into a cautionary tale. This is the trickiest part
Use this for manual upgrades via a standalone TFTP server . 2. Installation Methods Cisco Ip Phone 7965 Firmware Download
Always read the Cisco release notes to see if there is an intermediate "hop" version required before moving to the newest firmware.