Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

If a urlskip has multiple regexes, the second and beyond instances will be replaced with the first. This is due to a cache:
https://github.com/gorhill/uBlock/blob/74b838cc0367fc3d5d2e538325f9d85eec71615c/src/js/urlskip.js#L134-L138

I've confirmed in a debugger and this is definitely what's happening.

A specific URL where the issue occurs.

https://links.vinted.com/e/t/aHR0cHM6Ly93d3cudmludGVkLmNvLnVrL2UvaXRlbT9pZD0xMjM0NTY3ODkwfDAwMDAwMDAwLTAwMDAtMDAwMC0wMDAwLTAwMDAwMDAwMDAwMHxBMGFhYUFhYV9BMEEwQWFhQUFBYUFhQTAtYUFhYTBhYUFBQUFBQWFhQUFhPQ==

Steps to Reproduce

1. Add a filter ||links.vinted.com/e/t/$document
2. Add a filter ||links.vinted.com$document,urlskip=/\/e\/t\/([A-Za-z0-9=]+)/ -base64 /^(.*?)\|/
3. Go to the reproduction URL (matches the pattern of a real URL perfectly but anonymised)
4. Notice the link is blocked but no redirect URL is shown
5. Edit the second filter to ||links.vinted.com$document,urlskip=/\/e\/t\/([A-Za-z0-9=]+)/ -base64
6. Notice a redirect URL is shown
7. Notice the second regex should work fine
8. Revert to the original second filter, set a breakpoint on https://github.com/gorhill/uBlock/blob/74b838cc0367fc3d5d2e538325f9d85eec71615c/src/js/urlskip.js#L135 and notice /\/e\/t\/([A-Za-z0-9=]+)/ is used twice

Expected behavior

A redirect URL is shown of https://www.vinted.co.uk/e/item?id=1234567890.

Actual behavior

No redirect URL is shown.

uBO version

1.68.0

Browser name and version

Zen (1.17.15b)

Operating System and version

macOS