Rust

Extending one String with another is possible through .extend(s.chars()). However, this is better expressed using push_str(s).

It is unsafe to match untrusted input against regular expressions without ^ anchor. URLs with missing anchors can prove fatal as malicious inputs bypass the system's security checks.

.filter(..).next() is equivalent to .find(..). Prefer .find(..) for readability.

Consider using .clone_from() instead of assigning the result of .clone().

clone_from() may perform better in some cases because some structs may have custom implementations of clone_from(), which improve performance by avoiding needless allocations.

The std::mem module provides the take() method to acquire the current value and replace it with the default value of the same type. Prefer using this over mem::replace with T::default().

Comparing a floating point with NaN using == or != is redundant. NaN cannot be compared to anything, not even itself. Use .is_nan() instead.

Arc<RwLock<HashMap<K, V>>> has performance concerns, the dashmap crate provides a much better alternative to concurrent hashmaps. Hence, Arc<RwLock<HashMap<K, V>>> is better off replaced by Arc<DashMap<K, V>> from the dashmap crate.

Box::new(T::default()) is overly verbose, involving two function calls instead of one. It can be better written as Box::<T>::default().

In the standard library in Rust before 1.29.0, there is weak synchronization in the Arc::get_mut method. This synchronization issue can be lead to memory safety issues through race conditions.

In the standard library in Rust before 1.58.1, there is a race condition that enables symlink following. An attacker could take advantage of this security vulnerability to trick a privileged program into deleting files and directories the attacker couldn't otherwise access or delete.

This issue is raised when a hardcoded temporary file or directory is detected. Creating and using insecure temporary files can leave the application vulnerable to attacks. Lack of uniqueness in temporary files allows attackers to predict the filename and inject dangerous data into the application through the temporary file.

Certain cryptographic algorithms are known to be cryptographically insecure and should be avoided.

The strength of public-key-based cryptographic algorithm (like RSA) is determined by the time that it takes to derive the private key by using brute-force methods. 1024-bit keys are to be avoided since they are easy to brute-force. However, 2048-bit keys are said to be sufficient until 2030. Preferably use 4096-bit keys.

The caret symbol (^) in some languages is used to represent exponentiation. However, in Rust, as in many C-like languages, it represents the bitwise exclusive-or (XOR) operation. It is recommended to carefully vet if the caret is being used for XOR or exponentiation.

Redirects to a destination that is provided by the user or through an external function may be invalid or unsafe. Consider verifying the destination before firing the redirect.

The regex Rust library prior to version 1.5.5 is vulnerable to regular expression denial of service (ReDoS) attacks. Ensure that you use version 1.5.5 or above in Cargo.toml dependencies for regex.

Chained Ord::min and Ord::max functions can be replaced with Ord::clamp, which is also a more readable solution.

Checking if a value is None via a direct comparison is usually inspired from other programming languages (e.g. foo is None in Python). In Rust, the Eq trait is used to perform the comparison, which is unneeded. The Option type provides the is_none() and is_some() methods which return a boolean, allowing for more idoimatic comparison.

Using mem::replace(&mut _, mem::uninitialized()) or mem::replace(&mut _, mem::zeroed()) may lead to undefined behaviour even if the value is overwritten later, as the uninitialized value may remain in case of panic recovery.