This question's explanation and your answers so far.
クッキー (cookie) に関する記述 a～c のうち, 適切なものだけをすべて挙げたものはどれか。 a Web サイトを前回閲覧した際に入力した ID やパスワードなどは, 別の PC を使用して閲覧する場合でもクッキーで引き継がれるので再入力が要らない。 b インターネットカフェなどで一時的に PC を借用して Web サイトを閲覧したときは, 閲覧が終わったらクッキーを消去すべきである。 c クッキーに個人情報が保存されている場合, クロスサイトスクリプティングなどで, その個人情報が盗まれることがある。
This choice is wrong because it includes a. Cookies are stored in the browser of the PC used for browsing, so even if you open the same site on a different PC, the previous cookies do not exist there and the ID and password are not carried over. b is appropriate, but since a is not, this combination does not hold.
b and c are appropriate, but this choice is wrong because it also includes the inappropriate a. If you keep in mind the basic point that a cookie is stored locally per PC (per browser) and is not carried over from one device to another, you can rule out a.
This choice both includes the inappropriate a and leaves out the appropriate b, so it is wrong on two counts. Only c in it is correct, and the basic countermeasure of deleting cookies after using a shared PC (b) is missing.
正解 The correct answer is (エ) b, c. A cookie is a small piece of text data that a Web server has the browser keep, and it is stored locally inside the PC (browser) used for browsing. Because of this property, only b and c are correct. b: On a shared PC, such as one at an Internet cafe, cookies remain on that PC even after browsing ends. If they contain session information that keeps you logged in, or an input history, the next person who uses the PC could impersonate you and misuse it, so you should delete the cookies when you finish browsing. c: The value of a cookie can be read by scripts running in the browser, so if a malicious script is planted on a Web site that has a cross-site scripting (XSS) vulnerability, personal information or a session ID stored in the cookie may be sent to the attacker and stolen. On the other hand, a is wrong: because cookies are stored on the PC side, they are not carried over when you browse from a different PC. Therefore only the two statements b and c are appropriate, which gives (エ).