Percent Chance · Huntress CTF 2026

The challenge

My address bar is having a moment.

The question, word for word Days 1–6: decode the blob completely and submit the slug its final non-empty line names. Answer format: word-word-word-NN, trimmed. Mastery: 33 blobs.

Reading the prompt: what it said we'd need

Clue	What it pointed to	What I did about it
"My address bar"	Text as it appears in a URL: percent-encoding, where a byte is written `%` plus two hex digits	Nothing new: the decoder was added on Day 4, three days early
"Having a moment"	The URL is garbled, everything `%`-escaped	—
"Percent Chance" (the title)	A pun on "percent"	—
Mastery gains a line each day	Seven lines this time, the last in percent-encoding	Test seven-line blobs with the last line fully and partly encoded

What was in the files

%4e%69%63%65%20%77%6f%72%6b%20%64%65%63%6f%64%69%6e%67%20 …

Nice work decoding this warmup! To solve, submit this exact answer to the Game Master: witty-storm-fern-77

How to read percent-encoding by eye: it's hex with a % in front of each byte. %20 is a space, %2d a hyphen, %3a a colon. In real URLs usually only the unsafe characters are escaped (Nice%20work); here every single byte was, which is the "moment" the address bar is having.

Mode	Delivered as	Raw format
Single Solve	`blob.txt`, 318 B	Every byte as lowercase `%xx`
Time Trial	`blob.txt`, 333 B	The same
Mastery	One zip of `blob-01..33.txt` (16,362 B)	Seven labelled lines, one encoding from each day

A Mastery blob (blob-01), split seven ways:

Line	Encoding	Decodes to
`01`	Base64 (Day 1)	"Nice work decod"
`02`	ROT13 (Day 2)	"ing this warmup"
`03`	Hex (Day 3)	"! To solve, subm"
`04`	Binary (Day 4)	"it this exact a"
`05`	Decimal (Day 5)	"nswer to the Gam"
`06`	Octal (Day 6)	"e Master: eager"
`07`	Percent (Day 7)	"-island-petal-75"

The slug was split across the last two lines again ("eager" + "-island-petal-75"), as on Day 6. Since Day 6's edge-word fix, a fragment at a line boundary can't mislead the scorer.

Single Solve: CORRECT in 23 seconds

Started at 15:49:13 UTC. The solver read it in one percent layer: witty-storm-fern-77. CORRECT at 15:49:36, flag e27637f8…6086. Our solver reuses Day 4's decoders; its 4 tests passed before the timed runs, including seven-line blobs with the last line fully and partly encoded.

Time Trial: 1.41 s of a 7-second clock

started_at 2026-10-07T15:49:40.685Z  deadline 2026-10-07T15:49:47.685Z
  artifact blob.txt 333 bytes sha256 f3c0df26e5e8c520… (checked)
  message: happy-starfish-quartz-38
  start         469 ms
  artifact      320 ms
  solve           0 ms
  submit        617 ms
  TOTAL        1406 ms
result CORRECT  flag 1f55a336…e437

Mastery: 1.96 s of a 9-second clock, first attempt

started_at 2026-10-07T15:49:45.529Z  deadline 2026-10-07T15:49:54.529Z
  artifact warmups-day-07-mastery.zip 16362 bytes sha256 add5655a4f7ae68c… (checked)
  set1.message … set33.message (33 slugs)
  start         594 ms
  artifact      501 ms
  solve          51 ms
  submit        810 ms
  TOTAL        1955 ms
result CORRECT  flag caa3cace…78f9

33 seven-line blobs solved in 51 ms in total.

Time to solve

All three modes were solved in 33 s, from the Single Solve start at 15:49:13 UTC to the Mastery CORRECT at 15:49:47 UTC; each mode went through on the first submit, with the Time Trial taking 1.41 s of its 7 s and the Mastery 1.96 s of its 9 s.

The first week of warmups, in one table

Day	Challenge	New encoding	Mastery	Attempts to Mastery CORRECT
1	A Little Based	Base64	3 blobs	3 (delivery-shape bugs)
2	Half a Turn	ROT13	8 × 2 lines	1 (partly by luck)
3	Hex Appeal	Hex	13 × 3	1
4	Two of a Kind	Binary	18 × 4	3 (server 503; slug-only line)
5	By the Numbers	Decimal	23 × 5	1
6	Eight Is Enough	Octal	28 × 6	2 (word split at a line edge)
7	Percent Chance	Percent	33 × 7	1

Every failure became a permanent fix in the shared decoder: per-line decoding (Day 2's luck), the naturalness tie-breaker and combinations (Day 4), and edge-word scoring (Day 6).

Takeaways

Reading ahead finished the week early. Decimal, octal, and percent were added on Day 4 from the posted prompts. Days 5–7 each took about half a minute.
The shared decoder is the real product. Seven days of encodings and three hard-won scoring fixes live in one place, so each day's solver is a few lines.
Next week will likely add an eighth line. The pattern (one new encoding a day, one more Mastery line, five more blobs) has held for six days straight.