CTX-03　Invisible Unicode characters

block 2 hits here sandbox-verified

① What it stops

Invisible Unicode character detected (tag characters, zero-width, word joiner, BOM in middle of file)

Strip invisible characters; treat any occurrence in instructions as hostile until proven otherwise.

② Criteria

Item	Value
Severity	critical
Category	injection
Gate	Gate 1 content safety
Criterion type	file_content
Applies to	Read、Write、Edit、Bash

This rule does not use regex pattern matching.

Generated directly from rules/default.json — never hand-written or paraphrased.

③ Real hits

2026-09-24T01:44:35+08:00 ✗ block [CTX-03] tool: Write　exit code: 2 criterion: invisible_content hit: U+200B at offset 10

Triggered in a disposable sandbox project using the real hooks/pre_tool_use.py — the same method as challenge/generate_challenge.py. All 24 rules verified this way (24/24).

Daily ledger on this machine: 2 hits

2026-09-15T14:29:33+08:00 ✗ blocked [CTX-03] tool: Read　host: generic criterion: invisible_file_content U+200B at offset 25069

④ False positives & exemptions

Built-in exclude patterns are listed under ②. Four exemption mechanisms exist globally (declared workspace roots, policy path whitelist, path-suspect alert-only, exclude patterns); counts on this machine are published on the Chinese page and in Limits.

⑤ Boundaries

Boundary
Criterion type	file_content
Applies to	-
Platform	all platforms
Case sensitivity	Measured: insensitive (`RM -RF` is blocked like `rm -rf`)
Path normalisation	Measured: effective (`./sub/../.env` is blocked)
Scripts not parsed	An absolute path outside the project mentioned in a Bash command is alerted, not blocked — `scripts are not parsed (THREAT_MODEL Non-goals)`
Failure posture	fail-open; best-effort, not a hard security boundary

⑥ Reproduce

grep -h "CTX-03" .psl/audit/*.jsonl | head python challenge/generate_challenge.py python challenge/verify.py

Cite this page

Antinel AgentState. CTX-03 Invisible Unicode characters — rule detail. https://antinel.com/en/agentstate/rules/CTX-03/ (accessed YYYY-MM-DD)

Antinel. (2026). CTX-03 Invisible Unicode characters — rule detail. AgentState. https://antinel.com/en/agentstate/rules/CTX-03/

BibTeX

@misc{antinel_en_agentstate_rules_CTX_03,
  title        = {CTX-03 Invisible Unicode characters — rule detail},
  author       = {{Antinel}},
  year         = {2026},
  url          = {https://antinel.com/en/agentstate/rules/CTX-03/},
  note         = {claim tier: measured}
}

Claim tier: measured　采集时刻：2026-09-23T22:41:18+08:00