As part of 9.2.10.x release, default Jquery library used by Portal is upgraded from 1.12.4 version to 126.96.36.199 version to improve security posture of portals.
Potential Breaking Change
If you have custom javscript code in portal which is using Jquery API's which were deperecated or had a change in behavior in Jquery versions 1.3, 1.6, 1.7, 1.8 and 1.9, these API's will no longer work or will have a changed behavior as documented in Jquery documentation.
You can find more details about API's which were deprecated in Old Jquery versions here
Jquery 1.3 - https://api.jquery.com/category/deprecated/deprecated-1.3/
Jquery 1.6 - https://api.jquery.com/category/version/1.6/
Jquery 1.7 - https://api.jquery.com/category/deprecated/deprecated-1.7/
Jquery 1.8 - https://api.jquery.com/category/deprecated/deprecated-1.8/
Jquery 1.9 - https://api.jquery.com/category/deprecated/deprecated-1.9/
Most common API which had a behavior change in jquery 1.6 onwards is attr (https://api.jquery.com/attr/). This api returns undefined after Jquery 1.6+
How to Mitigate
Following are the options which you can utilize to resolve this issue.
You can also load the corresponding version of jquery which your API requires using portal webfiles. However, please ensure that you are utilizing jquery noconflict API (https://api.jquery.com/jquery.noconflict/) in order to ensure that there is no conflict with the jquery libraries loaded by default in portal.
This option is not recommended because older versions of Jquery libraries have known security vulnerabilities.