Back-port "fix: anchor tag safety" to 2.x

[bajtos]

Setting target="_blank" on anchor tags is unsafe unless used in conjunction with rel="noopener".

This is a back-port of dd3afdc (#4789) to fix the problem in version 2.x.

@shockey @JonathanParrilla PTAL

Description

I ran grep -r target src/main/template to find all places where we are creating links to external URLs and then fixed these places by adding rel="noopener noreferrer" attribute.

Motivation and Context

In LoopBack, we are depending on swagger-ui version 2.x (see https://github.com/strongloop/loopback-component-explorer). We tried to upgrade to 3.x, but found that such upgrade requires too much effort, and thus decided to stick with 2.x.

Now we are seeing a security vulnerability reported for our module. I believe we are not affected by the vulnerability, because the possibly-malicious URLs are fully under control of the person running swagger-ui, but it still look bad that security checkers are reporting a vulnerability.

Can we back-port the fix from 3.x to 2.x please?

How Has This Been Tested?

I tried to run npm test, unfortunately it failed with a cryptic error:

> swagger-ui@2.2.10 pretest /Users/bajtos/src/swagger-ui
> npm run jshint


> swagger-ui@2.2.10 prejshint /Users/bajtos/src/swagger-ui
> gulp

fs.js:27
const { Math, Object, Reflect } = primordials;
                                  ^

ReferenceError: primordials is not defined
    at fs.js:27:35
    at req_ (/Users/bajtos/src/swagger-ui/node_modules/natives/index.js:143:24)
    at Object.req [as require] (/Users/bajtos/src/swagger-ui/node_modules/natives/index.js:55:10)
    at Object.<anonymous> (/Users/bajtos/src/swagger-ui/node_modules/vinyl-fs/node_modules/graceful-fs/fs.js:1:37)
    at Module._compile (internal/modules/cjs/loader.js:759:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:770:10)
    at Module.load (internal/modules/cjs/loader.js:628:32)
    at Function.Module._load (internal/modules/cjs/loader.js:555:12)
    at Module.require (internal/modules/cjs/loader.js:666:19)
    at require (internal/modules/cjs/helpers.js:16:16)

I also try to run mocha directly, unfortunately that failed too in the test should have "Swagger UI" in title with no diagnostic messages :(

Could you please advise how can/should I test this change?

Screenshots (if appropriate):

n/a

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[b-admike]

I am not familiar with this codebase, but upon reading https://www.jitbit.com/alexblog/256-targetblank---the-most-underestimated-vulnerability-ever/, LGTM 👍

[shockey]

@bajtos, just acknowledging that I've seen this -- I've kicked off an internal discussion.

[bajtos]

@shockey thanks! ❤️

While you are discussing my pull request internally, could you please discuss back-port of #5190 too? If you are ok to accept back-ports of security fixes from 3.x to 2.x, then I'd like to contribute back-port of #5190 too.

[shockey]

we've decided to pass on this PR, along with any other requests for updates to swagger-ui@2.

the last version of swagger-ui@2 was released 895 days ago, and was deprecated with the release of swagger-ui@3.0.0, which happened 824 days ago.

the effort required to confidently push a security-related fix for a codebase that:

• has not been touched in years
• this team hasn't worked on before
• needs build tools that don't work in current (i.e., safe) versions of Node
• may have first-party security issues that have been addressed in more current versions of Swagger UI
• definitely has a few third-party security issues, because the dependencies are so out of date
• isn't otherwise supported or maintained (yet merging this would give the illusion of some level of ongoing security)

..outweighs the benefit of pushing out a fix.

for your part @bajtos, I understand the predicament you're in -- I see that LoopBack has a legacy/LTS version that is pretty well stuck with swagger-ui@2 due to heavy customization and integration.

since there's no easy out for you until your current version goes to EOL, feel free to fork our 2.x branch and create a forked module that includes these changes. I've had to do this with some of Swagger UI's dependencies for various reasons.

lastly, thanks for the PR. I do want to merge it, but I don't think it's the right thing to do given that it opens a Pandora's box of expectations for 2.x security updates going forward.

[bajtos]

@shockey thank you for a detailed explanation, I appreciate you took the time to discuss this matter in depth and write down your reasoning. I understand your situation. The decision you made makes sense, even if the consequences are not convenient to me :)