Смените пароль, отключите онлайн-платежи; никому не сообщайте код и реквизиты карты.

Because they are imperative forms addressed to:

• more than one person, or
• one person politely (like you in a formal notice)

So:

• смените = change
• отключите = disable / turn off

In warnings, instructions, and official messages, Russian often uses this polite/plural imperative.

Compare:

• смени пароль = change the password (informal, singular)
• смените пароль = change the password (polite or plural)

This is a very common aspect pattern in Russian.

• Смените and отключите are perfective imperatives.
  They tell someone to perform a single complete action:

  • change the password
  • disable online payments

• Не сообщайте is an imperfective negative imperative.
  With negative commands, Russian often prefers the imperfective to mean:

  • don’t do this
  • never do this
  • don’t be in the habit of doing this

So the sentence combines:

• Do these actions now/completely
• Do not ever do this

That is why the aspect changes.

Никому means to no one or more naturally in English, to anyone in a negative sentence.

It comes from никто = no one.

Its form here is dative case, because the verb сообщать / сообщить usually takes:

• the person told in the dative
• the information told in the accusative

So:

• никому не сообщайте = don’t tell anyone

Because сообщать does not need one for the person receiving the information.

Russian structure is:

• сообщать кому? что?
• tell someone something

So:

• кому? → никому
• что? → код и реквизиты карты

This is similar to English tell someone something, where someone also appears without a preposition.

Реквизиты means details / particulars / banking details.

In this context, реквизиты карты means something like:

• card details
• card information
• bank card details

It is a very common word in financial or official Russian. It does not mean requisites in the everyday English sense.

Examples of what реквизиты карты may include:

• card number
• expiry date
• cardholder name
• sometimes other identifying payment details

Because in Russian this word is very often used as a plural-only or mostly plural idea when talking about a set of details.

So реквизиты is natural because card details are understood as multiple pieces of information.

That is why Russian says:

• сообщать реквизиты карты
• указать банковские реквизиты

Even when English might say information as an uncountable noun, Russian often uses a plural noun here.

Because it depends on реквизиты:

• реквизиты чего? = details of what?
• карты = of the card

So:

• реквизиты карты = the card’s details / details of the card

This is a very common Russian noun + genitive pattern.

Other similar examples:

• номер телефона = phone number
• адрес банка = the bank’s address
• владелец карты = cardholder / owner of the card

Grammatically, карты directly modifies реквизиты:

• код и реквизиты карты

Literally, that looks like:

• the code and the card details

In real context, though, the meaning is clearly:

• the code and the card details
• in other words, both are related to the card/payment security situation

Russian often leaves some relationships implicit when the meaning is obvious.

If someone wanted to make it fully explicit, they might say something like:

• код карты и реквизиты карты

But that would sound repetitive. The original sentence is more natural.

Because Russian often uses the plural for a category of transactions or a feature that can be turned on/off.

So отключите онлайн-платежи means:

• disable online payments
• turn off online payment functionality

Even if English might sometimes say online payment as a general feature, Russian naturally uses the plural here.

The semicolon separates two closely connected parts:

1. Смените пароль, отключите онлайн-платежи
2. никому не сообщайте код и реквизиты карты

It is stronger than a comma, but not as final as a period. It helps show:

• first: urgent actions to take
• second: an important warning

Russian punctuation often uses semicolons this way in formal instructions, alerts, and notices.

Yes, Russian word order is flexible, but the original is natural and clear.

For example, you could also say:

• Код и реквизиты карты никому не сообщайте.

This puts more emphasis on what must not be shared.

The original:

• никому не сообщайте код и реквизиты карты

puts early emphasis on don’t tell anyone.

Both are grammatical, but the original sounds very normal for an official warning.

Yes, it sounds like a formal instruction or security warning.

Clues:

• imperative plural/polite forms: смените, отключите, не сообщайте
• official vocabulary: реквизиты
• concise, command-style phrasing

This is exactly the kind of Russian you might see in:

• a bank message
• a fraud alert
• a support chat warning
• a security notification

If you were speaking casually to one person, the forms would usually be:

• Смени пароль, отключи онлайн-платежи; никому не сообщай код и реквизиты карты.

So the changes are:

• смените → смени
• отключите → отключи
• не сообщайте → не сообщай

The meaning stays the same, but the tone becomes informal and singular.