这不是一个漏洞，而是一个没有写进文档的特性。

It's not a bug, it's an undocumented feature.

Source: Tatoeba

Sentence Composition

=1 这不 zhèbu (coll.) As a matter of fact, ... (used to introduce evidence for what one has just asserted)
=1 这不 zhèbù connects two clauses, emphasising how the following clause substantiates the preceding clause
=2 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=2 是 shì variant of 是 shì
=3 一个 yīge
  1. a; an; one
  2. the whole (afternoon, summer vacation etc)
=3 一个 yīgè
  1. Combination of the numeral 一 (“one”) and the generic classifier 個／个: a; an; one
  2. same
4 漏洞 lòudòng
  1. leak
  2. hole
  3. gap
  4. loophole
5 而是 érshì rather
=6 一个 yīge
  1. a; an; one
  2. the whole (afternoon, summer vacation etc)
=6 一个 yīgè
  1. Combination of the numeral 一 (“one”) and the generic classifier 個／个: a; an; one
  2. same
7 没有 méiyǒu
  1. haven't
  2. hasn't
  3. doesn't exist
  4. to not have
  5. to not be
=8 写 xiě to write
=8 写 xiè used in 寫意 xièyì
9 进 jìn
  1. to go forward
  2. to advance
  3. to go in
  4. to enter
  5. to put in
  6. to submit
  7. to take in
  8. to admit
  9. (math.) base of a number system
  10. classifier for sections in a building or residential compound
10 文档 wéndàng (computer) file; document; documentation
=11 的 de
  1. of; ~'s (possessive particle)
  2. (used after an attribute when it modifies a noun)
  3. (used at the end of a declarative sentence for emphasis)
  4. (used after a noun, verb or adjective to form a nominal expression, as in 皮革的 pígéde "one made of leather" or 跑堂兒的 pǎotángrde "a waiter (literally, one who runs back and forth in a restaurant)" or 新的 xīnde "new one")
  5. also pr. dì or di in poetry and songs
=11 的 dī a taxi; a cab (abbr. for 的士 dīshì)
=11 的 dí really and truly
=11 的 dì (bound form) bull's-eye; target
12 特性 tèxìng
  1. property
  2. characteristic