fix(isISO8601): only accept T or a space as the date-time separator

[yu2971512385-ui]

Fixes #2861.

The bug

The default pattern separates the date and time with [T\s]:

const iso8601 = /.../([T\s](...time...))?.../;

\s matches tab, newline, form feed, vertical tab and a non-breaking space in addition to a plain space, so all of them are accepted as ISO 8601 separators:

validator.isISO8601('2009-01-01\t00:00:00'); // true (tab)
validator.isISO8601('2009-01-01\n00:00:00'); // true (newline)
validator.isISO8601('2009-01-01\f00:00:00'); // true (form feed)
validator.isISO8601('2009-01-01\v00:00:00'); // true (vertical tab)

ISO 8601 permits only T; RFC 3339 §5.6 additionally allows a plain space (which is why the class accepts a space). No relevant specification allows the rest of \s. Accepting a newline is particularly undesirable, since it lets a two-line input pass a single-value check.

The fix

Narrow the class in the default pattern to [T ]. strictSeparator: true already uses [T] and is unchanged; the plain-space separator that RFC 3339 allows (e.g. 2009-05-19 14:39:22) keeps working.

Tests

Added a case asserting T and a space are accepted while tab, newline, form feed, vertical tab and a non-breaking space are rejected. Verified it fails on the unpatched source and passes with the fix; full npm test is green.

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (9ff3424) to head (3001b3a).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2892   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2599      2599           
  Branches       658       658           
=========================================
  Hits          2599      2599           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.