• fix(security): the nesting regexp no longer backtracks exponentially (ReDoS) on an unclosed $t(. Its repeated group had overlapping alternatives ([^()"']+ inside (?:...)*?, and inside parentheses [^()] also matched quotes), so a string containing $t( without a closing ) made the engine try every way to split the text: about 2x the runtime per extra character, and a ~25 character value hung t() for minutes. With the default config this was reachable through any interpolated value (t('greet', { name: '$t(aaaaaaaaaaaaaaaaaaaaaaaa' })): escaping does not touch $, t or (, and the skipOnVariables check runs the regexp on the interpolated result, so nest: false did not help either. Every alternative now starts with a different character (plain char, ", ' or (), so there is only one way to match and the cost is linear. Quoted strings and one level of parentheses in nesting options keep working (#2336). The only difference: a lone " or ' inside unquoted parentheses within $t(...) is no longer matched. Affects 25.3.3 to 26.4.3. Thanks to Anisetti Chaitanya Eshwar Prasad for the responsible disclosure.
• fix(security): nest() now resolves $t(...) in a single pass and no longer nests text that came out of a resolved value. Every nested lookup reset the shared nesting regexp, so the loop started over from the beginning of the string after each match. That had two effects. First, a $t(...) inside a variable that the nested lookup deliberately kept literal (default skipOnVariables: true) was resolved anyway by the outer loop: with outer: 'A $t(inner) B' and inner: 'Hi {{name}}', t('outer', { name: '$t(secret)' }) rendered the secret translation. It now stays A Hi $t(secret) B, the same as without the outer nesting; with skipOnVariables: false it is still resolved. Second, the cost was quadratic when an unclosed $t( preceded many nestings, which matters when an app passes untrusted input as the key itself (t(userInput)): 20,000 nestings took ~1.4 s, now ~25 ms. The resolved value is now sliced into the result instead of going through String.replace, so $&, $`, $' and $$ stay literal as before (26.4.2).