Potential fix for code scanning alert no. 33: Client-side cross-site scripting

[Dargon789]

Potential fix for https://github.com/Dargon789/mempool/security/code-scanning/33

To fix the problem, ensure only permitted paths are ever used in window.location.replace. Rather than interpolating the user-provided params.next in the resulting URL, use the whitelisted version from the path array after validation. Refuse to use any value not in the allowed list. Specifically, in handleDemoRedirect, change the redirect line to use the validated value (params.next must be in path, so use the whitelisted entry directly for redirection) and never trust user input for the base URL. This prevents injection of a malicious value.

Edit file frontend/src/app/shared/common.utils.ts:

• On line 233, change window.location.replace(`${params.next}?next=${nextPath}`) to use the whitelisted value (window.location.replace(${path[index]}?next=${nextPath}))
• No new imports are required.

Suggested fixes powered by Copilot Autofix. Review carefully before merging.

Summary by Sourcery

Bug Fixes:

• Prevent client-side XSS by using validated whitelisted paths in window.location.replace instead of untrusted user input.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

This PR fixes a client-side XSS vulnerability in handleDemoRedirect by ensuring the redirection URL uses only a whitelisted path entry instead of the untrusted params.next value.

Sequence diagram for secure redirect in handleDemoRedirect

sequenceDiagram
participant User
participant "handleDemoRedirect()"
participant "window.location.replace()"
User->>"handleDemoRedirect()": Triggers redirect with params.next
"handleDemoRedirect()"->>"handleDemoRedirect()": Validate params.next against whitelist (path[])
alt params.next is in whitelist
    "handleDemoRedirect()"->>"window.location.replace()": Redirect to whitelisted path[index]?next=nextPath
else params.next is not in whitelist
    "handleDemoRedirect()"->>User: No redirect (or error)
end

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File-Level Changes

Change	Details	Files
Use validated whitelist entry for window.location.replace to prevent XSS	Replaced window.location.replace interpolation of params.next with the whitelisted path[index] Kept nextPath logic unchanged	frontend/src/app/shared/common.utils.ts

Possibly linked issues

• compare br Master fix work flow non poof jop e2e cypress don't truest google chome & dev google nodejs cloud verify POW POR POA. #37: The PR fixes the frontend redirect URL logic, replacing params.next with path[index] to prevent client-side XSS, as described in the issue.

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