Links created by URSA take you to this source. This is a single html file containing all the code and instructions. You can read the code if you want by typing ctrl-U (ctrl-opt-U on Macs). You can also check the authenticity of the code you got by doing this:
1. Head to Online-convert.com and write https://passlok.com/ursa in the second box from the top, then type Enter or click "Convert File". This will instruct this website to fetch the URSA code from its server and perform a SHA256 operation on it. Alternatively, you can obtain the SHA256 of the source code you displayed with ctrl-U and saved afterwards with a local utility or a different online resource.
2. A new screen should appear, displaying the SHA256 string in several formats. Now you want to compare this with the published value, which is available at different places, including below. If both strings are the same, the code is tamper-free. Here are a few locations where this string in published:
Current version of URSA is: 4.2.1
Made on 9/6/17
Main source: https://passlok.com/ursa
SHA256 string for web source (single html file):
see the author reading this: https://www.youtube.com/watch?v=FI-uiodIRvc
URSA is open-source, which means that you can participate in its development. It is hosted on GitHub, at https://github.com/fruiz500/ursa
The code at this source is split into parts rather than all together in one file, in order to facilitate reading and editing it. Libraries contributed by others have their own folder, and any edits made to them are duly noted. The code can be executed through this link:https://fruiz500.github.io/ursa. The single-file production version is essentially identical to the GitHub version, except that all files are combined into one in order to make it easy to verify its authenticity, as described above.
This is the preferred venue for suggestions, posting about bugs, and even contributing bits of code. To do this, open an issue or ask for a pull request if you have found a solution to a given problem.
Many thanks in advance.
Extension for Chrome or Firefox
There is a third way to get it, and this is loaded as a browser extension or addon, which has the advantage that the browser web store keeps the code safe (if you trust Google or Mozilla, that is). Another advantage is that what you do in the extension tab cannot be seen by other extensions, whereas what you do in a regular web page can indeed be seen.
Here's the link to the Chrome web store, and to the Firefox web store.