What's the link to download Web Agent 12.8?
At first glance, there's no Web Agent 12.6, 12.7, or 12.8 available. For version 12.8, an embedded Web Agent comes with CA Access Gateway (SPS) 12.6, 12.7, and 12.8.
For a Web Agent only, the latest one available on December 19th, 2022 is 12.52SP1CR11 (1).
Note that Web Agent 12.52SP1CR11 is compatible with Policy Server 12.8 as per the Support Matrix (2).
(1)
SSO WEBAGENT R12.52 SP01 CR11 [#2820]
ca-wa-12.52-sp01-cr11-aix-64.zip
ca-wa-12.52-sp01-cr11-aix.zip
ca-wa-12.52-sp01-cr11-hpux-itan-64.zip
ca-wa-12.52-sp01-cr11-hpux-itan.zip
ca-wa-12.52-sp01-cr11-linux-x86-64.zip
ca-wa-12.52-sp01-cr11-linux.zip
ca-wa-12.52-sp01-cr11-sol-64.zip
ca-wa-12.52-sp01-cr11-sol-x86-64.zip
ca-wa-12.52-sp01-cr11-sol-x86.zip
ca-wa-12.52-sp01-cr11-sol.zip
ca-wa-12.52-sp01-cr11-win32.zip
ca-wa-12.52-sp01-cr11-win64-64.zip
ca-wa-12.52-sp01-cr11-zLinux-64.zip
(2)
Symantec SiteMinder (previously CA Single Sign-On) 12.8
4.1 Policy Server and Agents Compatibility
SiteMinder Policy Server 12.8 supports previous versions of Agents and
Access Gateways (previously called Secure Proxy Server) with the
following caveats:
Any 6.x versions of Web Agents, Access Gateways (previously called
Secure Proxy Server), ERP Agents, ASA Agents, and 5.x versions of ERP
Agents that are not beyond their end-of-service date do not support
IPv6 or FIPS Mode (and can only connect to 12.8 Policy Server in FIPS
Compatibility Mode).